| 0/0 |
2026/08/15 19:27 |
flow |
assessment-kcsan |
29m
Results: map[Benign:true Explanation:### Race Summary
`acpi_ut_trace_ptr` vs `acpi_ut_trace_ptr` on global variable
`acpi_gbl_nesting_level`.
### Synchronization Context
`acpi_ut_trace_ptr` is called locklessly during ACPICA debug tracing (e.g., via
`ACPI_FUNCTION_TRACE_PTR`) upon entering ACPICA internal functions. When
concurrent tasks execute ACPI device probing or table lookups across multiple
CPUs, they both invoke `acpi_ut_trace_ptr()` and update `acpi_gbl_nesting_level`
concurrently without mutual exclusion locks.
### Final Classification
**BENIGN**
### Reasoning
`acpi_gbl_nesting_level` is purely a diagnostic/debug counter maintained by
ACPICA to track procedure call nesting depth and update the statistic
`acpi_gbl_deepest_nesting`.
In the Linux kernel driver build (`#ifndef ACPI_APPLICATION`),
`acpi_gbl_nesting_level` is not even included in standard debug printouts (it is
only printed in userland utilities like `acpi_exec` / `iASL`). The counter is
completely decoupled from kernel logic, control flow, locking, memory
management, or hardware interactions. Concurrent lossy updates or torn reads on
`acpi_gbl_nesting_level` have zero effect on functional system behavior or
correctness.
### Recommended Annotations
To suppress KCSAN reports on ACPICA debug tracing counters:
- Wrap updates in `data_race()` macro (e.g.
`data_race(acpi_gbl_nesting_level++)` and
`data_race(acpi_gbl_nesting_level--)`).]
|
| 1/1 |
2026/08/15 19:27 |
action |
kernel-checkouter |
1m
Results: map[KernelSrc:/app/workdir/cache/src/a22070ff955cd31b75d6fdec27c3c1e30655e00e]
|
| 2/1 |
2026/08/15 19:28 |
action |
kernel-builder |
9m
Results: map[KernelObj:/app/workdir/cache/build/b9d1e2510f61ab7582c91bdc7af5b6052066880c]
|
| 3/1 |
2026/08/15 19:37 |
action |
codesearch-prepare |
7m
Results: map[Index:codesearch-index]
|
| 4/1 |
2026/08/15 19:45 |
agent |
expert |
11m
Model:
Results:
Instruction: # KCSAN Data Race Severity Analysis Protocol
You are an expert Linux kernel concurrency engineer analyzing a Kernel
Concurrency Sanitizer (KCSAN) data race report to determine if it is
**BENIGN** or **HARMFUL**.
## 1. CLASSIFICATIONS
### **BENIGN (Truly Benign)**
The logic is sound and structurally tolerant to compiler optimizations or
stale/torn reads.
- **Diagnostics/Stats:** Reads used only for `/proc`, `/sys`, counters, or
`pr_info`.
- **Heuristic Hints:** A "hint" flag where an old value only causes a
slightly delayed update or a sub-optimal but safe fast-path.
- **Single-Writer Flag Updates:** A single writer updating flags where the
concurrent read is a simple bitwise check (e.g., `flags & MASK`). These are
historically tolerated, assuming neither "Fused Accesses" nor "Ordering
Violations" are relevant in this context.
- **Marked Reloads:** A load feeding into a `cmpxchg()` loop or checked
against a later `READ_ONCE()` reload.
- **Safe Overwrites:** Writing the same value already present.
### **HARMFUL (Logic Bug or Marking Required)**
The race causes incorrect behavior due to a synchronization failure or
because missing annotations allow the compiler to break the algorithm.
**Marking Required for Correctness:**
The algorithm is logically sound but requires annotations (`READ_ONCE()`,
`WRITE_ONCE()`, `smp_load_acquire()`, `smp_store_release()`, etc.) to be safe.
- **Fused Accesses:** The compiler might merge accesses or hoist a load out
of a loop, breaking polling/wait loops (livelocks).
- **Torn Accesses:** A large access (e.g., 64-bit on 32-bit arch) might be
split into multiple non-atomic accesses. Note that `READ_ONCE()` does **not**
guarantee atomicity for 64-bit variables on 32-bit architectures.
- **Ordering Violations:** The race breaks a "happens-before" relationship
(requires primitives with implied or explicit memory barriers).
**Logic Bugs:**
A fundamental synchronization failure. Marking accesses will **not** fix it;
the logic itself must change.
- **Pointers/Lifecycle:** The racing variable is a pointer being dereferenced
or a refcount governing object lifecycle (Use-After-Free risk).
- **Control Flow:** The variable guards a critical section, memory allocation,
or hardware command.
- **Bitfields:** Concurrent writes to different bits in the same word.
Compilers often use non-atomic read-modify-write sequences, meaning a
write to `bit_A` can "clobber" a concurrent write to `bit_B`. However,
do not blindly assume all bitfield accesses are harmful; you must prove
that a concurrent write actually clobbers another in a way that breaks
logic.
- **Complex Structures:** Races on shared lists, trees, or hashmaps.
- **Lossy Updates:** Concurrent plain RMW operations (e.g., `var++`) on
non-diagnostic variables where every increment must be preserved.
- **State Machines:** Races allowing a state machine to bypass transitions
or enter an invalid state.
- **Adjacent Unsynchronized Operations:** Consider races happening at the
same time. For example, if both threads execute `struct->has_elements = true;
list_add(node, &struct->list);`, the race on `has_elements` implies an
adjacent race on `list_head`, which is HARMFUL.
## 2. RESEARCH & ANALYSIS WORKFLOW
1. **Locate the Race:** Find the exact variables and functions in the stack
traces. Do not speculate about hypothetical compiler
behaviors or theoretical dangers (e.g., dismissing something as
"fundamentally unsafe") without tracing the actual data flow to a crash.
2. **Contextualize:** Identify held locks, RCU sections, or interrupt
contexts. Explain why the race is possible (e.g., "Thread A holds `lock`,
but Thread B is a lockless reader").
3. **Data Flow:** Follow the racing variable into its subsequent uses. If
the reader sees a stale or torn value, what branch is taken? Does it lead
to a pointer dereference or `BUG_ON()`? **You must prove harm via this
data flow.**
4. **Failure Sequencing (if HARMFUL):** Construct a two-column execution trace
demonstrating the failure.
*Example format:*
```text
CPU0 CPU1
function_a()
// lockless read
ptr = global_ptr
<PREEMPT>
function_b()
lock(&my_lock)
global_ptr = NULL
unlock(&my_lock)
kfree(ptr)
if (ptr)
*ptr = 1; // -> Use-After-Free!
```
## 3. OUTPUT FORMAT
- **Race Summary:** `[Function A]` vs `[Function B]` on `[Variable/Field]`.
- **Synchronization context:** List held locks and explain the lack of mutual
exclusion.
- **Final Classification:** **BENIGN** or **HARMFUL**.
**If BENIGN:**
- **Reasoning:** Briefly explain why the race is structurally tolerant to stale
or torn reads.
- **Recommended Annotations:** Suggest appropriate annotations (e.g.,
`READ_ONCE()`, `data_race()`).
**If HARMFUL:**
- **Failure Reasoning:** Explain and provide a two-column interleaving showing
exactly how the race leads to a failure such as corruption or kernel crash.
- **Recommended Fix (ONLY if fix is trivial):** Suggest a structural fix (e.g.,
"Hold `mapping->i_pages` lock", "Convert to `atomic_t`") or required memory
ordering annotations (e.g., "Wrap in `READ_ONCE()`", "Use
`smp_load_acquire()`").
Don't make assumptions about the kernel source code (it may be different from what you assume it is).
Extensively use the provided code access tools (codesearch-*, git-*, grepper, etc)
to examine the actual source code, and confirm any assumptions.
Prefer calling several tools at the same time to save round-trips.
Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.
Prompt:
The data race report is:
==================================================================
BUG: KCSAN: data-race in acpi_ut_trace_ptr / acpi_ut_trace_ptr
read-write to 0xffffffff89410638 of 4 bytes by task 30 on cpu 1:
acpi_ut_trace_ptr+0x49/0x180 drivers/acpi/acpica/utdebug.c:306
acpi_ns_handle_to_pathname+0x3b/0x1d0 drivers/acpi/acpica/nsnames.c:138
acpi_rs_create_pci_routing_table+0x41a/0x760 drivers/acpi/acpica/rscreate.c:314
acpi_rs_get_prt_method_data+0xa3/0x100 drivers/acpi/acpica/rsutils.c:456
acpi_get_irq_routing_table+0x98/0xe0 drivers/acpi/acpica/rsxface.c:137
acpi_pci_irq_find_prt_entry+0xb3/0x6e0 drivers/acpi/pci_irq.c:215
acpi_pci_irq_lookup+0x3e/0x330 drivers/acpi/pci_irq.c:299
acpi_pci_irq_enable+0x13a/0x3d0 drivers/acpi/pci_irq.c:414
pcibios_enable_device+0x88/0xa0 arch/x86/pci/common.c:699
do_pci_enable_device+0x152/0x2d0 drivers/pci/pci.c:1998
pci_enable_device_flags+0x348/0x3a0 drivers/pci/pci.c:2089
pci_enable_device+0x1a/0xa0 drivers/pci/pci.c:2122
i801_probe+0x288/0xbf0 drivers/i2c/busses/i2c-i801.c:1573
local_pci_probe drivers/pci/pci-driver.c:332 [inline]
pci_call_probe drivers/pci/pci-driver.c:394 [inline]
__pci_device_probe drivers/pci/pci-driver.c:455 [inline]
pci_device_probe+0x28b/0x510 drivers/pci/pci-driver.c:489
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x1ba/0x600 drivers/base/dd.c:706
__driver_probe_device+0x14f/0x1c0 drivers/base/dd.c:868
driver_probe_device+0x37/0x2f0 drivers/base/dd.c:898
__driver_attach_async_helper+0xb6/0x130 drivers/base/dd.c:1224
async_run_entry_fn+0x52/0x180 kernel/async.c:129
process_one_work kernel/workqueue.c:3322 [inline]
process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3405
worker_thread+0x569/0x750 kernel/workqueue.c:3486
kthread+0x221/0x270 kernel/kthread.c:436
ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
read-write to 0xffffffff89410638 of 4 bytes by task 49 on cpu 0:
acpi_ut_trace_ptr+0x49/0x180 drivers/acpi/acpica/utdebug.c:306
acpi_ns_build_normalized_path+0x43/0x420 drivers/acpi/acpica/nsnames.c:202
acpi_ns_get_pathname_length+0x3f/0x70 drivers/acpi/acpica/nsnames.c:65
acpi_rs_get_pci_routing_table_length+0x1f2/0x2b0 drivers/acpi/acpica/rscalc.c:817
acpi_rs_create_pci_routing_table+0x79/0x760 drivers/acpi/acpica/rscreate.c:201
acpi_rs_get_prt_method_data+0xa3/0x100 drivers/acpi/acpica/rsutils.c:456
acpi_get_irq_routing_table+0x98/0xe0 drivers/acpi/acpica/rsxface.c:137
acpi_pci_irq_find_prt_entry+0xb3/0x6e0 drivers/acpi/pci_irq.c:215
acpi_pci_irq_lookup+0x3e/0x330 drivers/acpi/pci_irq.c:299
acpi_pci_irq_enable+0x13a/0x3d0 drivers/acpi/pci_irq.c:414
pcibios_enable_device+0x88/0xa0 arch/x86/pci/common.c:699
do_pci_enable_device+0x152/0x2d0 drivers/pci/pci.c:1998
pci_enable_device_flags+0x348/0x3a0 drivers/pci/pci.c:2089
pci_enable_device+0x1a/0xa0 drivers/pci/pci.c:2122
i801_probe+0x288/0xbf0 drivers/i2c/busses/i2c-i801.c:1573
local_pci_probe drivers/pci/pci-driver.c:332 [inline]
pci_call_probe drivers/pci/pci-driver.c:394 [inline]
__pci_device_probe drivers/pci/pci-driver.c:455 [inline]
pci_device_probe+0x28b/0x510 drivers/pci/pci-driver.c:489
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x1ba/0x600 drivers/base/dd.c:706
__driver_probe_device+0x14f/0x1c0 drivers/base/dd.c:868
driver_probe_device+0x37/0x2f0 drivers/base/dd.c:898
__driver_attach_async_helper+0xb6/0x130 drivers/base/dd.c:1224
async_run_entry_fn+0x52/0x180 kernel/async.c:129
process_one_work kernel/workqueue.c:3322 [inline]
process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3405
worker_thread+0x569/0x750 kernel/workqueue.c:3486
kthread+0x221/0x270 kernel/kthread.c:436
ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
value changed: 0x0000000c -> 0x0000000e
Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 49 Comm: kworker/u8:3 Not tainted syzkaller #0 PREEMPT(lazy)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: async async_run_entry_fn
==================================================================
ACPI: \_SB_.LNKA: Enabled at IRQ 11
i801_smbus 0000:00:05.0: SMBus base address uninitialized, upgrade BIOS
Reply: ### Race Summary
`acpi_ut_trace_ptr` vs `acpi_ut_trace_ptr` on global variable `acpi_gbl_nesting_level`.
### Synchronization Context
`acpi_ut_trace_ptr` is called locklessly during ACPICA debug tracing (e.g., via `ACPI_FUNCTION_TRACE_PTR`) upon entering ACPICA internal functions. When concurrent tasks execute ACPI device probing or table lookups across multiple CPUs, they both invoke `acpi_ut_trace_ptr()` and update `acpi_gbl_nesting_level` concurrently without mutual exclusion locks.
### Final Classification
**BENIGN**
### Reasoning
`acpi_gbl_nesting_level` is purely a diagnostic/debug counter maintained by ACPICA to track procedure call nesting depth and update the statistic `acpi_gbl_deepest_nesting`.
In the Linux kernel driver build (`#ifndef ACPI_APPLICATION`), `acpi_gbl_nesting_level` is not even included in standard debug printouts (it is only printed in userland utilities like `acpi_exec` / `iASL`). The counter is completely decoupled from kernel logic, control flow, locking, memory management, or hardware interactions. Concurrent lossy updates or torn reads on `acpi_gbl_nesting_level` have zero effect on functional system behavior or correctness.
### Recommended Annotations
To suppress KCSAN reports on ACPICA debug tracing counters:
- Wrap updates in `data_race()` macro (e.g. `data_race(acpi_gbl_nesting_level++)` and `data_race(acpi_gbl_nesting_level--)`).
|
| 5/2 |
2026/08/15 19:45 |
llm |
expert |
0m
Model:
Tokens:
input: 7439
output: 41
thoughts: 143
Thoughts: **Analyzing a KCSAN Data Race Report**
Okay, so I've got this KCSAN data race report staring me in the face: `BUG: KCSAN: data-race in acpi_ut_trace_ptr / acpi_ut_trace_ptr`. The report indicates a read-write data race, which means two operations are accessing the same memory location, one of which is a write. Specifically, it's hitting 0xffffffff89410638, a 4-byte chunk. And the culprit function, `acpi_ut_trace_ptr`, is at the center of it all. It seems this is in the ACPI component which isn't a surprise. Data races in ACPI can be tricky to nail down.
The report also gives me the exact line number: `drivers/acpi/acpica/utdebug.c:306`. Right, so the logical first step is to dive into that code. I need to understand what's happening around that line. My focus will be on the memory accesses around the line specified. It's time to open up the source file and see what `acpi_ut_trace_ptr` is actually doing, and what its context is. I'm expecting some sort of logging or debugging related code, judging from the function name. From there, I can figure out what kind of data the race is happening on, and begin formulating hypotheses about the conflicting access patterns. I'll be looking for shared data structures, concurrent tasks, and any locking primitives that might be missing or misused. Time to dig in!
|
| 6/2 |
2026/08/15 19:45 |
tool |
read-file |
0m
Args: map[File:drivers/acpi/acpica/utdebug.c FirstLine:280 LineCount:50]
Results: map[Contents: 280:
281: ACPI_EXPORT_SYMBOL(acpi_ut_trace)
282:
283: /*******************************************************************************
284: *
285: * FUNCTION: acpi_ut_trace_ptr
286: *
287: * PARAMETERS: line_number - Caller's line number
288: * function_name - Caller's procedure name
289: * module_name - Caller's module name
290: * component_id - Caller's component ID
291: * pointer - Pointer to display
292: *
293: * RETURN: None
294: *
295: * DESCRIPTION: Function entry trace. Prints only if TRACE_FUNCTIONS bit is
296: * set in debug_level
297: *
298: ******************************************************************************/
299: void
300: acpi_ut_trace_ptr(u32 line_number,
301: const char *function_name,
302: const char *module_name,
303: u32 component_id, const void *pointer)
304: {
305:
306: acpi_gbl_nesting_level++;
307: acpi_ut_track_stack_ptr();
308:
309: /* Check if enabled up-front for performance */
310:
311: if (ACPI_IS_DEBUG_ENABLED(ACPI_LV_FUNCTIONS, component_id)) {
312: acpi_debug_print(ACPI_LV_FUNCTIONS,
313: line_number, function_name, module_name,
314: component_id, "%s %p\n",
315: acpi_gbl_function_entry_prefix, pointer);
316: }
317: }
318:
319: /*******************************************************************************
320: *
321: * FUNCTION: acpi_ut_trace_str
322: *
323: * PARAMETERS: line_number - Caller's line number
324: * function_name - Caller's procedure name
325: * module_name - Caller's module name
326: * component_id - Caller's component ID
327: * string - Additional string to display
328: *
329: * RETURN: None
]
|
| 7/2 |
2026/08/15 19:45 |
llm |
expert |
0m
Model:
Tokens:
input: 8703
output: 60
thoughts: 44
Thoughts: Okay, let's dive into this. Here's how I'd approach understanding `acpi_gbl_nesting_level`:
**Investigating `acpi_gbl_nesting_level`**
Right, my immediate instinct is to dissect `acpi_gbl_nesting_level`. Given my experience, I'm already forming some preliminary hypotheses. This likely involves some form of nested control structures or a system for managing the depth of execution within the ACPI (Advanced Configuration and Power Interface) framework. To get a handle on its actual purpose and context, I need to see *where* it's being used. So, the first step is clear: I'm going to conduct a thorough search for all references to `acpi_gbl_nesting_level`. That should give me a good overview of how it's being manipulated and in what kinds of scenarios. Once I see its usage, I can start forming a clear picture.
|
| 8/2 |
2026/08/15 19:45 |
tool |
codesearch-find-references |
0m
Args: map[ContextFile:drivers/acpi/acpica/utdebug.c IncludeSnippetLines:5 Name:acpi_gbl_nesting_level SourceTreePrefix:]
Results: map[References:<nil> TruncatedOutput:false]
|
| 9/2 |
2026/08/15 19:45 |
llm |
expert |
0m
Model:
Tokens:
input: 9029
output: 42
thoughts: 128
Thoughts: **Analyzing ACPI Nesting Level References**
Okay, so I need to understand how `acpi_gbl_nesting_level` is being used. First, I'll go through the references to it. I see that it's in `drivers/acpi/acpica/utdebug.c`. Instead of just grabbing a snippet or using grep, I'm going to take a more focused approach.
I'll start by reading the code around each instance of `acpi_gbl_nesting_level` in `drivers/acpi/acpica/utdebug.c`. That should give me the immediate context. To start, I'll focus on lines 200 through 380, since I can infer a rough range based on the function calls surrounding the variable's usage.
|
| 10/2 |
2026/08/15 19:45 |
tool |
read-file |
0m
Args: map[File:drivers/acpi/acpica/utdebug.c FirstLine:200 LineCount:100]
Results: map[Contents: 200: va_start(args, format);
201: acpi_os_vprintf(format, args);
202: va_end(args);
203: }
204:
205: ACPI_EXPORT_SYMBOL(acpi_debug_print)
206:
207: /*******************************************************************************
208: *
209: * FUNCTION: acpi_debug_print_raw
210: *
211: * PARAMETERS: requested_debug_level - Requested debug print level
212: * line_number - Caller's line number
213: * function_name - Caller's procedure name
214: * module_name - Caller's module name
215: * component_id - Caller's component ID
216: * format - Printf format field
217: * ... - Optional printf arguments
218: *
219: * RETURN: None
220: *
221: * DESCRIPTION: Print message with no headers. Has same interface as
222: * debug_print so that the same macros can be used.
223: *
224: ******************************************************************************/
225: void ACPI_INTERNAL_VAR_XFACE
226: acpi_debug_print_raw(u32 requested_debug_level,
227: u32 line_number,
228: const char *function_name,
229: const char *module_name,
230: u32 component_id, const char *format, ...)
231: {
232: va_list args;
233:
234: /* Check if debug output enabled */
235:
236: if (!ACPI_IS_DEBUG_ENABLED(requested_debug_level, component_id)) {
237: return;
238: }
239:
240: va_start(args, format);
241: acpi_os_vprintf(format, args);
242: va_end(args);
243: }
244:
245: ACPI_EXPORT_SYMBOL(acpi_debug_print_raw)
246:
247: /*******************************************************************************
248: *
249: * FUNCTION: acpi_ut_trace
250: *
251: * PARAMETERS: line_number - Caller's line number
252: * function_name - Caller's procedure name
253: * module_name - Caller's module name
254: * component_id - Caller's component ID
255: *
256: * RETURN: None
257: *
258: * DESCRIPTION: Function entry trace. Prints only if TRACE_FUNCTIONS bit is
259: * set in debug_level
260: *
261: ******************************************************************************/
262: void
263: acpi_ut_trace(u32 line_number,
264: const char *function_name,
265: const char *module_name, u32 component_id)
266: {
267:
268: acpi_gbl_nesting_level++;
269: acpi_ut_track_stack_ptr();
270:
271: /* Check if enabled up-front for performance */
272:
273: if (ACPI_IS_DEBUG_ENABLED(ACPI_LV_FUNCTIONS, component_id)) {
274: acpi_debug_print(ACPI_LV_FUNCTIONS,
275: line_number, function_name, module_name,
276: component_id, "%s\n",
277: acpi_gbl_function_entry_prefix);
278: }
279: }
280:
281: ACPI_EXPORT_SYMBOL(acpi_ut_trace)
282:
283: /*******************************************************************************
284: *
285: * FUNCTION: acpi_ut_trace_ptr
286: *
287: * PARAMETERS: line_number - Caller's line number
288: * function_name - Caller's procedure name
289: * module_name - Caller's module name
290: * component_id - Caller's component ID
291: * pointer - Pointer to display
292: *
293: * RETURN: None
294: *
295: * DESCRIPTION: Function entry trace. Prints only if TRACE_FUNCTIONS bit is
296: * set in debug_level
297: *
298: ******************************************************************************/
299: void
]
|
| 11/2 |
2026/08/15 19:45 |
llm |
expert |
0m
Model:
Tokens:
input: 10802
output: 42
thoughts: 22
Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience:
**Diving into `utdebug.c` for ACPI Analysis**
Okay, time to dig deeper. I'm going to navigate directly into the `drivers/acpi/acpica/utdebug.c` file. This is where the ACPI Component Architecture (ACPICA) utility debug code resides, and based on the current troubleshooting context, it's likely going to offer valuable insights. I anticipate finding functions related to trace logging, error reporting, and potentially assertion handling. I'm specifically looking for any clues that could shed light on the recent ACPI-related issue I'm chasing. Understanding how the debugging infrastructure is implemented within ACPICA itself is often crucial for pinpointing the root cause of these complex ACPI problems. It is my understanding of this module that should give me a better understanding of the issues. Hopefully, this file holds the key to the next debugging step.
|
| 12/2 |
2026/08/15 19:45 |
tool |
read-file |
0m
Args: map[File:drivers/acpi/acpica/utdebug.c FirstLine:350 LineCount:100]
Results: map[Contents: 350: component_id, "%s %s\n",
351: acpi_gbl_function_entry_prefix, string);
352: }
353: }
354:
355: /*******************************************************************************
356: *
357: * FUNCTION: acpi_ut_trace_u32
358: *
359: * PARAMETERS: line_number - Caller's line number
360: * function_name - Caller's procedure name
361: * module_name - Caller's module name
362: * component_id - Caller's component ID
363: * integer - Integer to display
364: *
365: * RETURN: None
366: *
367: * DESCRIPTION: Function entry trace. Prints only if TRACE_FUNCTIONS bit is
368: * set in debug_level
369: *
370: ******************************************************************************/
371:
372: void
373: acpi_ut_trace_u32(u32 line_number,
374: const char *function_name,
375: const char *module_name, u32 component_id, u32 integer)
376: {
377:
378: acpi_gbl_nesting_level++;
379: acpi_ut_track_stack_ptr();
380:
381: /* Check if enabled up-front for performance */
382:
383: if (ACPI_IS_DEBUG_ENABLED(ACPI_LV_FUNCTIONS, component_id)) {
384: acpi_debug_print(ACPI_LV_FUNCTIONS,
385: line_number, function_name, module_name,
386: component_id, "%s %08X\n",
387: acpi_gbl_function_entry_prefix, integer);
388: }
389: }
390:
391: /*******************************************************************************
392: *
393: * FUNCTION: acpi_ut_exit
394: *
395: * PARAMETERS: line_number - Caller's line number
396: * function_name - Caller's procedure name
397: * module_name - Caller's module name
398: * component_id - Caller's component ID
399: *
400: * RETURN: None
401: *
402: * DESCRIPTION: Function exit trace. Prints only if TRACE_FUNCTIONS bit is
403: * set in debug_level
404: *
405: ******************************************************************************/
406:
407: void
408: acpi_ut_exit(u32 line_number,
409: const char *function_name,
410: const char *module_name, u32 component_id)
411: {
412:
413: /* Check if enabled up-front for performance */
414:
415: if (ACPI_IS_DEBUG_ENABLED(ACPI_LV_FUNCTIONS, component_id)) {
416: acpi_debug_print(ACPI_LV_FUNCTIONS,
417: line_number, function_name, module_name,
418: component_id, "%s\n",
419: acpi_gbl_function_exit_prefix);
420: }
421:
422: if (acpi_gbl_nesting_level) {
423: acpi_gbl_nesting_level--;
424: }
425: }
426:
427: ACPI_EXPORT_SYMBOL(acpi_ut_exit)
428:
429: /*******************************************************************************
430: *
431: * FUNCTION: acpi_ut_status_exit
432: *
433: * PARAMETERS: line_number - Caller's line number
434: * function_name - Caller's procedure name
435: * module_name - Caller's module name
436: * component_id - Caller's component ID
437: * status - Exit status code
438: *
439: * RETURN: None
440: *
441: * DESCRIPTION: Function exit trace. Prints only if TRACE_FUNCTIONS bit is
442: * set in debug_level. Prints exit status also.
443: *
444: ******************************************************************************/
445: void
446: acpi_ut_status_exit(u32 line_number,
447: const char *function_name,
448: const char *module_name,
449: u32 component_id, acpi_status status)
]
|
| 13/2 |
2026/08/15 19:45 |
llm |
expert |
0m
Model:
Tokens:
input: 12528
output: 24
thoughts: 246
Thoughts: **Analyzing the Scope of `acpi_gbl_nesting_level`**
Okay, let's dive into this `acpi_gbl_nesting_level` variable. I need to understand its usage across the entire codebase. First, I'll leverage the tools at my disposal - I'll run a quick codesearch to find its definition and then immediately check all the references.
Wait a minute, let's step back and refine that. Before I get bogged down in a broader search, I'll focus in. I'll take a quick look at that returned list of references I've got already. Ah, here we are: `drivers/acpi/acpica/utdebug.c`.
It's being incremented in several debug-related functions like `acpi_gbl_nesting_level++` at lines 268, 306, 343, and 378, as well as a decrement and check. Okay, that's interesting. It looks like it's tracking a nesting level, likely for some sort of debug output or tracing. Now, I should make sure that this is the *only* use. There could be other, less obvious references. I'll employ `grepper` to be thorough, just to cover all bases and ensure I have a complete picture of its usage throughout the kernel.
|
| 14/2 |
2026/08/15 19:45 |
tool |
grepper |
0m
Args: map[Expression:acpi_gbl_nesting_level]
Results: map[Output:drivers/acpi/acpica/acglobal.h=196=ACPI_GLOBAL(u32, acpi_gbl_deepest_nesting);
drivers/acpi/acpica/acglobal.h:197:ACPI_INIT_GLOBAL(u32, acpi_gbl_nesting_level, 0);
drivers/acpi/acpica/acglobal.h-198-#endif
--
drivers/acpi/acpica/utdebug.c=60=void acpi_ut_track_stack_ptr(void)
--
drivers/acpi/acpica/utdebug.c-72-
drivers/acpi/acpica/utdebug.c:73: if (acpi_gbl_nesting_level > acpi_gbl_deepest_nesting) {
drivers/acpi/acpica/utdebug.c:74: acpi_gbl_deepest_nesting = acpi_gbl_nesting_level;
drivers/acpi/acpica/utdebug.c-75- }
--
drivers/acpi/acpica/utdebug.c=134=acpi_debug_print(u32 requested_debug_level,
--
drivers/acpi/acpica/utdebug.c-163- acpi_gbl_previous_thread_id = thread_id;
drivers/acpi/acpica/utdebug.c:164: acpi_gbl_nesting_level = 0;
drivers/acpi/acpica/utdebug.c-165- }
--
drivers/acpi/acpica/utdebug.c-183-
drivers/acpi/acpica/utdebug.c:184: fill_count = 48 - acpi_gbl_nesting_level -
drivers/acpi/acpica/utdebug.c-185- strlen(acpi_ut_trim_function_name(function_name));
--
drivers/acpi/acpica/utdebug.c-190- acpi_os_printf("[%02d] %*s",
drivers/acpi/acpica/utdebug.c:191: acpi_gbl_nesting_level, acpi_gbl_nesting_level + 1, " ");
drivers/acpi/acpica/utdebug.c-192- acpi_os_printf("%s%*s: ",
--
drivers/acpi/acpica/utdebug.c=263=acpi_ut_trace(u32 line_number,
--
drivers/acpi/acpica/utdebug.c-267-
drivers/acpi/acpica/utdebug.c:268: acpi_gbl_nesting_level++;
drivers/acpi/acpica/utdebug.c-269- acpi_ut_track_stack_ptr();
--
drivers/acpi/acpica/utdebug.c=300=acpi_ut_trace_ptr(u32 line_number,
--
drivers/acpi/acpica/utdebug.c-305-
drivers/acpi/acpica/utdebug.c:306: acpi_gbl_nesting_level++;
drivers/acpi/acpica/utdebug.c-307- acpi_ut_track_stack_ptr();
--
drivers/acpi/acpica/utdebug.c=337=acpi_ut_trace_str(u32 line_number,
--
drivers/acpi/acpica/utdebug.c-341-
drivers/acpi/acpica/utdebug.c:342: acpi_gbl_nesting_level++;
drivers/acpi/acpica/utdebug.c-343- acpi_ut_track_stack_ptr();
--
drivers/acpi/acpica/utdebug.c=373=acpi_ut_trace_u32(u32 line_number,
--
drivers/acpi/acpica/utdebug.c-377-
drivers/acpi/acpica/utdebug.c:378: acpi_gbl_nesting_level++;
drivers/acpi/acpica/utdebug.c-379- acpi_ut_track_stack_ptr();
--
drivers/acpi/acpica/utdebug.c=408=acpi_ut_exit(u32 line_number,
--
drivers/acpi/acpica/utdebug.c-421-
drivers/acpi/acpica/utdebug.c:422: if (acpi_gbl_nesting_level) {
drivers/acpi/acpica/utdebug.c:423: acpi_gbl_nesting_level--;
drivers/acpi/acpica/utdebug.c-424- }
--
drivers/acpi/acpica/utdebug.c=446=acpi_ut_status_exit(u32 line_number,
--
drivers/acpi/acpica/utdebug.c-470-
drivers/acpi/acpica/utdebug.c:471: if (acpi_gbl_nesting_level) {
drivers/acpi/acpica/utdebug.c:472: acpi_gbl_nesting_level--;
drivers/acpi/acpica/utdebug.c-473- }
--
drivers/acpi/acpica/utdebug.c=495=acpi_ut_value_exit(u32 line_number,
--
drivers/acpi/acpica/utdebug.c-509-
drivers/acpi/acpica/utdebug.c:510: if (acpi_gbl_nesting_level) {
drivers/acpi/acpica/utdebug.c:511: acpi_gbl_nesting_level--;
drivers/acpi/acpica/utdebug.c-512- }
--
drivers/acpi/acpica/utdebug.c=534=acpi_ut_ptr_exit(u32 line_number,
--
drivers/acpi/acpica/utdebug.c-547-
drivers/acpi/acpica/utdebug.c:548: if (acpi_gbl_nesting_level) {
drivers/acpi/acpica/utdebug.c:549: acpi_gbl_nesting_level--;
drivers/acpi/acpica/utdebug.c-550- }
--
drivers/acpi/acpica/utdebug.c=571=acpi_ut_str_exit(u32 line_number,
--
drivers/acpi/acpica/utdebug.c-584-
drivers/acpi/acpica/utdebug.c:585: if (acpi_gbl_nesting_level) {
drivers/acpi/acpica/utdebug.c:586: acpi_gbl_nesting_level--;
drivers/acpi/acpica/utdebug.c-587- }
]
|
| 15/2 |
2026/08/15 19:45 |
llm |
expert |
0m
Model:
Tokens:
input: 14915
output: 41
thoughts: 41
Thoughts: Okay, let's dive into this. Here's my take on examining `utdebug.c`:
**Deep Dive into `utdebug.c` (Lines 50-200)**
Alright, so I'm focusing in on `utdebug.c`. Let's get right into it, specifically lines 50 through 200. This section is where things usually start getting interesting in these debug utilities. I'll be looking for the core logic, any potential optimizations or, more likely given the nature of debug code, any particularly tricky error handling or conditional compilation directives. I'm already anticipating seeing some macros, perhaps some function pointer assignments, or maybe even some custom data structures specific to the debugging framework. I'm going to want to understand how it interfaces with the ACPI subsystem and how granular the debugging controls are. Any unusual naming conventions or clever uses of bit flags will jump out at me immediately. Ultimately, my goal is to grasp the fundamental operational principles of this debug module within the context of the larger ACPI architecture. I expect a few edge cases here, I'm ready to find them.
|
| 16/2 |
2026/08/15 19:45 |
tool |
read-file |
0m
Args: map[File:drivers/acpi/acpica/utdebug.c FirstLine:50 LineCount:100]
Results: map[Contents: 50: * FUNCTION: acpi_ut_track_stack_ptr
51: *
52: * PARAMETERS: None
53: *
54: * RETURN: None
55: *
56: * DESCRIPTION: Save the current CPU stack pointer
57: *
58: ******************************************************************************/
59:
60: void acpi_ut_track_stack_ptr(void)
61: {
62: acpi_size current_sp;
63:
64: if (¤t_sp < acpi_gbl_lowest_stack_pointer) {
65: #pragma GCC diagnostic push
66: #if defined(__GNUC__) && __GNUC__ >= 12
67: #pragma GCC diagnostic ignored "-Wdangling-pointer="
68: #endif
69: acpi_gbl_lowest_stack_pointer = ¤t_sp;
70: #pragma GCC diagnostic pop
71: }
72:
73: if (acpi_gbl_nesting_level > acpi_gbl_deepest_nesting) {
74: acpi_gbl_deepest_nesting = acpi_gbl_nesting_level;
75: }
76: }
77:
78: /*******************************************************************************
79: *
80: * FUNCTION: acpi_ut_trim_function_name
81: *
82: * PARAMETERS: function_name - Ascii string containing a procedure name
83: *
84: * RETURN: Updated pointer to the function name
85: *
86: * DESCRIPTION: Remove the "Acpi" prefix from the function name, if present.
87: * This allows compiler macros such as __func__ to be used
88: * with no change to the debug output.
89: *
90: ******************************************************************************/
91:
92: static const char *acpi_ut_trim_function_name(const char *function_name)
93: {
94:
95: /* All Function names are longer than 4 chars, check is safe */
96:
97: if (*(ACPI_CAST_PTR(u32, function_name)) == ACPI_PREFIX_MIXED) {
98:
99: /* This is the case where the original source has not been modified */
100:
101: return (function_name + 4);
102: }
103:
104: if (*(ACPI_CAST_PTR(u32, function_name)) == ACPI_PREFIX_LOWER) {
105:
106: /* This is the case where the source has been 'linuxized' */
107:
108: return (function_name + 5);
109: }
110:
111: return (function_name);
112: }
113:
114: /*******************************************************************************
115: *
116: * FUNCTION: acpi_debug_print
117: *
118: * PARAMETERS: requested_debug_level - Requested debug print level
119: * line_number - Caller's line number (for error output)
120: * function_name - Caller's procedure name
121: * module_name - Caller's module name
122: * component_id - Caller's component ID
123: * format - Printf format field
124: * ... - Optional printf arguments
125: *
126: * RETURN: None
127: *
128: * DESCRIPTION: Print error message with prefix consisting of the module name,
129: * line number, and component ID.
130: *
131: ******************************************************************************/
132:
133: void ACPI_INTERNAL_VAR_XFACE
134: acpi_debug_print(u32 requested_debug_level,
135: u32 line_number,
136: const char *function_name,
137: const char *module_name,
138: u32 component_id, const char *format, ...)
139: {
140: acpi_thread_id thread_id;
141: va_list args;
142: #ifdef ACPI_APPLICATION
143: int fill_count;
144: #endif
145:
146: /* Check if debug output enabled */
147:
148: if (!ACPI_IS_DEBUG_ENABLED(requested_debug_level, component_id)) {
149: return;
]
|
| 17/2 |
2026/08/15 19:45 |
llm |
expert |
0m
Model:
Tokens:
input: 16602
output: 41
thoughts: 55
Thoughts: Here's my take on the thought process, as requested:
**Diving into `acpi_debug_print` and Nesting Levels**
Okay, let's get down to brass tacks. I need to understand how `acpi_gbl_nesting_level` is being leveraged within the `acpi_debug_print` function. The best way to do that, as always, is to go directly to the source. Specifically, I need to check out lines 150 through 200 of `drivers/acpi/acpica/utdebug.c`. That should give me the relevant context. I'm expecting to see how this global variable influences the output β likely in the form of indentation, prefixes, or some other mechanism to indicate the current level of nested function calls. It's crucial, in debugging ACPI, to visually parse the call stack to grasp the control flow. Seeing how this variable is used, I should be able to deduce how the debug output is structured based on the current level of nesting. Knowing this, will help me debug ACPI systems. I am looking for the usage pattern to be apparent, so the function call structure makes sense. Let's see what's there...
|
| 18/2 |
2026/08/15 19:45 |
tool |
read-file |
0m
Args: map[File:drivers/acpi/acpica/utdebug.c FirstLine:150 LineCount:50]
Results: map[Contents: 150: }
151:
152: /*
153: * Thread tracking and context switch notification
154: */
155: thread_id = acpi_os_get_thread_id();
156: if (thread_id != acpi_gbl_previous_thread_id) {
157: if (ACPI_LV_THREADS & acpi_dbg_level) {
158: acpi_os_printf
159: ("\n**** Context Switch from TID %u to TID %u ****\n\n",
160: (u32)acpi_gbl_previous_thread_id, (u32)thread_id);
161: }
162:
163: acpi_gbl_previous_thread_id = thread_id;
164: acpi_gbl_nesting_level = 0;
165: }
166:
167: /*
168: * Display the module name, current line number, thread ID (if requested),
169: * current procedure nesting level, and the current procedure name
170: */
171: acpi_os_printf("%9s-%04d ", module_name, line_number);
172:
173: #ifdef ACPI_APPLICATION
174: /*
175: * For acpi_exec/iASL only, emit the thread ID and nesting level.
176: * Note: nesting level is really only useful during a single-thread
177: * execution. Otherwise, multiple threads will keep resetting the
178: * level.
179: */
180: if (ACPI_LV_THREADS & acpi_dbg_level) {
181: acpi_os_printf("[%u] ", (u32)thread_id);
182: }
183:
184: fill_count = 48 - acpi_gbl_nesting_level -
185: strlen(acpi_ut_trim_function_name(function_name));
186: if (fill_count < 0) {
187: fill_count = 0;
188: }
189:
190: acpi_os_printf("[%02d] %*s",
191: acpi_gbl_nesting_level, acpi_gbl_nesting_level + 1, " ");
192: acpi_os_printf("%s%*s: ",
193: acpi_ut_trim_function_name(function_name), fill_count,
194: " ");
195:
196: #else
197: acpi_os_printf("%-22.22s: ", acpi_ut_trim_function_name(function_name));
198: #endif
199:
]
|
| 19/2 |
2026/08/15 19:45 |
llm |
expert |
0m
Model:
Tokens:
input: 17781
output: 25
thoughts: 360
Thoughts: **Analyzing ACPICA Nesting Level in Kernel Debugging**
Okay, so I'm looking at this comment in `drivers/acpi/acpica/utdebug.c`, and it's pointing out how the nesting level is handled differently for the `acpi_exec/iASL` tools versus the Linux kernel. Specifically, inside the kernel, the debug tracing functions like `ACPI_FUNCTION_TRACE` increment `acpi_gbl_nesting_level`, call `acpi_ut_track_stack_ptr()`, and that function updates `acpi_gbl_deepest_nesting` if the current level is deeper. Now, the comment states that this nesting level is only useful for single-threaded executions, and I concur with that.
So, I need to figure out how `acpi_gbl_nesting_level` and `acpi_gbl_deepest_nesting` are actually *used* within the kernel code. Are they simply diagnostic metrics, or are they being used to control behavior, even if it's just for debugging purposes? I don't see anything obvious to indicate any meaningful use, however I'd like to check if they're used to track depth of calls, or other debug info that's critical.
Time to run a thorough search across the entire kernel codebase and see where these global variables are referenced. A grep, or better yet, a cross-reference search, should tell the tale. Let's see if we can find any relevant usage.
|
| 20/2 |
2026/08/15 19:45 |
tool |
grepper |
0m
Args: map[Expression:acpi_gbl_deepest_nesting]
Results: map[Output:drivers/acpi/acpica/acglobal.h=195=ACPI_GLOBAL(acpi_size *, acpi_gbl_lowest_stack_pointer);
drivers/acpi/acpica/acglobal.h:196:ACPI_GLOBAL(u32, acpi_gbl_deepest_nesting);
drivers/acpi/acpica/acglobal.h-197-ACPI_INIT_GLOBAL(u32, acpi_gbl_nesting_level, 0);
--
drivers/acpi/acpica/dbstats.c=308=acpi_status acpi_db_display_statistics(char *type_arg)
--
drivers/acpi/acpica/dbstats.c-497- acpi_os_printf("Deepest Procedure Nesting %u\n",
drivers/acpi/acpica/dbstats.c:498: acpi_gbl_deepest_nesting);
drivers/acpi/acpica/dbstats.c-499-#endif
--
drivers/acpi/acpica/utdebug.c=60=void acpi_ut_track_stack_ptr(void)
--
drivers/acpi/acpica/utdebug.c-72-
drivers/acpi/acpica/utdebug.c:73: if (acpi_gbl_nesting_level > acpi_gbl_deepest_nesting) {
drivers/acpi/acpica/utdebug.c:74: acpi_gbl_deepest_nesting = acpi_gbl_nesting_level;
drivers/acpi/acpica/utdebug.c-75- }
]
|
| 21/2 |
2026/08/15 19:45 |
llm |
expert |
0m
Model:
Tokens:
input: 18923
output: 22
thoughts: 129
Thoughts: **Analyzing ACPICA Debugging Macro Usage in the Kernel**
Okay, let's dive into how these ACPICA debug functions are actually leveraged within the kernel codebase. My initial thought is to examine how the `ACPI_FUNCTION_TRACE_PTR` or comparable macros are implemented and used. I'm thinking, when one of those macros is triggered β for instance, in a function like `acpi_ns_handle_to_pathname` or `acpi_ns_build_normalized_path` β the execution flow should lead directly into either `acpi_ut_trace_ptr` or `acpi_ut_trace`.
Now, I want to trace back and pinpoint the exact calls to `acpi_ut_trace_ptr`. The most efficient approach here is to use the `grepper` tool, and do a quick search within the relevant codebase to identify all instances where `acpi_ut_trace_ptr` is directly invoked. This should give me a solid overview of where this tracing mechanism is being actively used.
|
| 22/2 |
2026/08/15 19:45 |
tool |
grepper |
0m
Args: map[Expression:acpi_ut_trace_ptr]
Results: map[Output:drivers/acpi/acpica/acutils.h=303=void
drivers/acpi/acpica/acutils.h:304:acpi_ut_trace_ptr(u32 line_number,
drivers/acpi/acpica/acutils.h-305- const char *function_name,
--
drivers/acpi/acpica/utdebug.c=281=ACPI_EXPORT_SYMBOL(acpi_ut_trace)
--
drivers/acpi/acpica/utdebug.c-284- *
drivers/acpi/acpica/utdebug.c:285: * FUNCTION: acpi_ut_trace_ptr
drivers/acpi/acpica/utdebug.c-286- *
--
drivers/acpi/acpica/utdebug.c=299=void
drivers/acpi/acpica/utdebug.c:300:acpi_ut_trace_ptr(u32 line_number,
drivers/acpi/acpica/utdebug.c-301- const char *function_name,
--
include/acpi/acoutput.h-342-#define ACPI_FUNCTION_TRACE_PTR(name, pointer) \
include/acpi/acoutput.h:343: ACPI_TRACE_ENTRY (name, acpi_ut_trace_ptr, void *, pointer)
include/acpi/acoutput.h-344-
]
|
| 23/2 |
2026/08/15 19:45 |
llm |
expert |
0m
Model:
Tokens:
input: 19665
output: 27
thoughts: 1621
Thoughts: **Analyzing the Concurrency Issue with acpi_gbl_nesting_level**
Okay, so I'm looking at this trace and it seems like we have a potential race condition involving `acpi_gbl_nesting_level` in the ACPICA code. This is a global variable, initialized to zero, and it gets incremented upon entering certain ACPICA internal functions like `acpi_ut_trace_ptr` and decremented upon exiting using functions like `acpi_ut_exit`. This variable is managed by debug features and function trace macros, and my initial thought is, "Ah, this could get hairy if multiple tasks are hitting ACPICA code concurrently."
So, I need to understand the impact of this concurrent access. I'm thinking, this variable is likely used for debugging information and nothing more, I'll need to confirm if it has any effect on control flow, memory, or device state. I'll need to be thorough; I've already grepped the codebase, but I need to double-check.
I quickly scan the places where `acpi_gbl_nesting_level` is used in `acglobal.h` and `utdebug.c`. As suspected, it's used only for debug output formatting, specifically tracking function nesting depth within ACPICA. I see it's incremented in trace functions and decremented in exit functions. `acpi_ut_track_stack_ptr()` uses it to track `acpi_gbl_deepest_nesting`, which is itself printed in the debugger. There's some conditional code under `ACPI_APPLICATION`, but that's not relevant to the kernel driver.
Alright, that's it. It's strictly a debug counter, no functional code is relying on it. My analysis confirms this, and I can be sure that this variable is ONLY used for diagnostics.
Now, let me recall the benign vs harmful races guidelines. "Diagnostics/Stats: Reads used only for /proc, /sys, counters, or pr_info." "BENIGN (Truly Benign): The logic is sound and structurally tolerant to compiler optimizations or stale/torn reads. Diagnostics/Stats: Reads used only for /proc, /sys, counters, or pr_info."
Wait! There were concurrent accesses reported. Let me dive deeper into the code around those updates. I see that multiple tasks, in this case, Task 30 and Task 49, were concurrently calling `acpi_ut_trace_ptr` during ACPI resource probing on different CPUs. This means both tasks were incrementing the global `acpi_gbl_nesting_level`. The report clearly shows this concurrent read-write.
Since `acpi_gbl_nesting_level` is only a debug counter, even with concurrent modification, there's no impact on system operation, device drivers, or memory safety. The worst-case scenario is that the nesting level printed in the debug output might be inaccurate.
Finally, just to be thorough, I will need to check the Git history just in case. It's unlikely, but it's always good to be thorough and verify if there were prior discussions or fixes related to this kind of issue.
|
| 24/2 |
2026/08/15 19:46 |
tool |
git-log |
10m
Error:
Args: map[CodeRegexp:acpi_gbl_nesting_level]
Results:
|
| 25/2 |
2026/08/15 19:56 |
llm |
expert |
0m
Model:
Tokens:
input: 22029
output: 38
thoughts: 16
Thoughts: Here's my thought process, as if I were thinking it:
**Analyzing the ACPI Driver Codebase**
Okay, so I need to dig into the ACPI drivers. Where's the best place to start? My initial instinct is to go directly to the source - the git history. To keep the search focused, and given that I know the directory structure, I'll leverage `git log` and the `PathPrefix` option. This will allow me to target only commits that touch files within the `drivers/acpi/` directory. That approach should let me zero in quickly on relevant changes, recent work, and perhaps even some bug fixes or feature additions I might have missed. I figure this targeted approach will be far more efficient than a broad keyword search. Time to execute that command!
|
| 26/2 |
2026/08/15 19:56 |
tool |
git-log |
0m
Args: map[CodeRegexp:acpi_gbl_nesting_level PathPrefix:drivers/acpi/]
Results: map[Output:6e875fa0480c ACPICA: Debugger: fix slight indentation issue
6be2d72b1864 ACPICA: Update for a few debug output statements
4857a94de17a ACPICA: Fix deconstification warnings (-Wcast-qual) with function traces.
3aa0b085f62f ACPICA: Cleanup/improve global variable declarations.
bf9b448ef843 ACPICA: Debug output: Do not emit function nesting level for kernel build.
f540fadf29a6 ACPICA: Fix unmerged debugger divergences.
e2f7a7772880 ACPICA: hide private headers
4be44fcd3bf6 [ACPI] Lindent all ACPI files
0c9938cc7505 [ACPI] ACPICA 20050729 from Bob Moore
f9f4601f331a ACPICA 20050708 from Bob Moore <robert.moore@intel.com>
]
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| 27/2 |
2026/08/15 19:56 |
llm |
expert |
0m
Model:
Tokens:
input: 22513
output: 25
thoughts: 18
Thoughts: Okay, here's my interpretation of that thought process, assuming I'm deep in my domain:
**Analyzing Commit bf9b448ef843**
Alright, time to dig in. The first thing that pops into my head is, "Let's check commit `bf9b448ef843`!". No preamble, no fluff β I'm heading straight to the meat of things. This means I've probably got a hunch about something, or I'm on a specific track and this commit is the next logical point in my investigation. I'm likely interested in a specific change, a potential bug fix, or maybe just the implementation of a particular feature. I need to get in there and review the code, understand the rationale behind the changes, and see how it interacts with the broader system. Let's see what that commit brings to the table.
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| 28/2 |
2026/08/15 19:56 |
tool |
git-show |
0m
Args:
Results: map[Output:commit bf9b448ef8430548d0608a38ebddbf7f6ca14ed1
Author: Bob Moore <robert.moore@intel.com>
Date: Thu Nov 21 12:17:20 2013 +0800
ACPICA: Debug output: Do not emit function nesting level for kernel build.
The nesting level is really only useful during a single-thread
execution. Therefore, only enable this output for the AcpiExec
utility. Also, only emit the thread ID when executing under AcpiExec.
(Context switches are still detected and a message is emitted.)
ACPICA BZ 972.
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/drivers/acpi/acpica/utdebug.c b/drivers/acpi/acpica/utdebug.c
index 1a67b3944b3b..03ae8affe48f 100644
--- a/drivers/acpi/acpica/utdebug.c
+++ b/drivers/acpi/acpica/utdebug.c
@@ -185,6 +185,7 @@ acpi_debug_print(u32 requested_debug_level,
}
acpi_gbl_prev_thread_id = thread_id;
+ acpi_gbl_nesting_level = 0;
}
/*
@@ -193,13 +194,21 @@ acpi_debug_print(u32 requested_debug_level,
*/
acpi_os_printf("%9s-%04ld ", module_name, line_number);
+#ifdef ACPI_EXEC_APP
+ /*
+ * For acpi_exec only, emit the thread ID and nesting level.
+ * Note: nesting level is really only useful during a single-thread
+ * execution. Otherwise, multiple threads will keep resetting the
+ * level.
+ */
if (ACPI_LV_THREADS & acpi_dbg_level) {
acpi_os_printf("[%u] ", (u32)thread_id);
}
- acpi_os_printf("[%02ld] %-22.22s: ",
- acpi_gbl_nesting_level,
- acpi_ut_trim_function_name(function_name));
+ acpi_os_printf("[%02ld] ", acpi_gbl_nesting_level);
+#endif
+
+ acpi_os_printf("%-22.22s: ", acpi_ut_trim_function_name(function_name));
va_start(args, format);
acpi_os_vprintf(format, args);
@@ -420,7 +429,9 @@ acpi_ut_exit(u32 line_number,
component_id, "%s\n", acpi_gbl_fn_exit_str);
}
- acpi_gbl_nesting_level--;
+ if (acpi_gbl_nesting_level) {
+ acpi_gbl_nesting_level--;
+ }
}
ACPI_EXPORT_SYMBOL(acpi_ut_exit)
@@ -467,7 +478,9 @@ acpi_ut_status_exit(u32 line_number,
}
}
- acpi_gbl_nesting_level--;
+ if (acpi_gbl_nesting_level) {
+ acpi_gbl_nesting_level--;
+ }
}
ACPI_EXPORT_SYMBOL(acpi_ut_status_exit)
@@ -504,7 +517,9 @@ acpi_ut_value_exit(u32 line_number,
ACPI_FORMAT_UINT64(value));
}
- acpi_gbl_nesting_level--;
+ if (acpi_gbl_nesting_level) {
+ acpi_gbl_nesting_level--;
+ }
}
ACPI_EXPORT_SYMBOL(acpi_ut_value_exit)
@@ -540,7 +555,9 @@ acpi_ut_ptr_exit(u32 line_number,
ptr);
}
- acpi_gbl_nesting_level--;
+ if (acpi_gbl_nesting_level) {
+ acpi_gbl_nesting_level--;
+ }
}
#endif
]
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| 29/2 |
2026/08/15 19:56 |
llm |
expert |
0m
Model:
Tokens:
input: 23974
output: 15
thoughts: 737
Thoughts: **My Analysis of the `acpi_gbl_nesting_level` Race Condition**
Okay, so I've been looking at this potential data race involving `acpi_gbl_nesting_level`. The commit `bf9b448ef843` flagged this, and, as an expert in this area, I can see why. Let's break it down methodically.
First, I looked at the code and quickly confirmed the initial observations. The commit is right: `acpi_gbl_nesting_level` is essentially a debug counter, and a pretty rudimentary one at that. It's updated only during entry and exit of traced ACPI functions through calls to `acpi_ut_trace*` functions β which makes it a potential race condition. Also, as the original commit noted, it's not even used for outputting debugging information in a standard kernel build. It's really only there for single-threaded execution, or when compiling with debug flags.
So, I ran through my checklist to make a judgment:
1. **Critical Section Impact:** Is this variable read or modified in any logic that's critical or has any influence on the core functionality? No. It's purely for debug tracing, and is not within any lock's scope.
2. **Crash/Corruption Potential:** Can a stale or lossy update to this variable cause a crash or memory corruption? Absolutely not. It's just a 32-bit integer that tracks the call depth for debugging and stats β a worst-case scenario is an inaccurate nesting depth count.
3. **BENIGN Classification:** Does this qualify as "BENIGN"? Absolutely! It's purely for diagnostics and statistics, which aligns perfectly with the criteria. The "single-writer flag updates / heuristic hints / diagnostics / stats" classification is spot on.
Now, let's summarize my findings:
* **Race:** The potential race is between the `acpi_ut_trace*` calls that are reading and updating `acpi_gbl_nesting_level`.
* **Synchronization Context:** These `acpi_ut_trace*` calls happen locklessly within ACPICA function tracing. Because of the asynchronous execution of ACPI operations (like PCI device probing) this can happen on multiple CPUs concurrently.
* **Classification: BENIGN** - No impact on core functionality
* **Reasoning:** The counter is merely for debug information, which is a key factor in making a safe classification. Even if the value becomes incorrect, it doesn't affect the kernel's behaviour in any way.
Finally, while the race is benign, I think it is worth adding in some data-race annotations. It's worth considering using `data_race()` or `READ_ONCE()`/`WRITE_ONCE()` when accessing `acpi_gbl_nesting_level`. This will silence any KCSAN warnings on this debug data. I should also consider using `data_race(acpi_gbl_nesting_level++)` or `data_race(acpi_gbl_nesting_level--)` when incrementing/decrementing to suppress warnings on those lines.
I think I've covered everything. Time to verify with the set-results tool.
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2026/08/15 19:56 |
tool |
set-results |
0m
Args:
Results:
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| 31/2 |
2026/08/15 19:56 |
llm |
expert |
0m
Model:
Tokens:
input: 25442
output: 375
thoughts: 122
Thoughts: **Report Writing Time!**
Alright, the `set-results` call is done, which means it's go time to craft the detailed report. Time to switch gears and translate these results into something useful. I need to make sure I adhere to the established format; it's always crucial to be organized and methodical.
Let's quickly run through the sections to ensure I haven't missed anything: Race Summary comparing Function A and Function B on the specific Variable/Field, the Synchronization context where I need to list held locks and explain why mutual exclusion wasn't required. Then, the Final Classification is BENIGN, as expected. The Reasoning section will concisely explain *why* this race is structurally tolerant to stale or torn reads - thatβs the key here. And finally, the Recommended Annotations section.
Okay, everything seems completely clear and thorough. I'm satisfied. Now I can start formulating the final response.
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| 32/1 |
2026/08/15 19:56 |
action |
format-explanation |
0m
Results: map[Explanation:### Race Summary
`acpi_ut_trace_ptr` vs `acpi_ut_trace_ptr` on global variable
`acpi_gbl_nesting_level`.
### Synchronization Context
`acpi_ut_trace_ptr` is called locklessly during ACPICA debug tracing (e.g., via
`ACPI_FUNCTION_TRACE_PTR`) upon entering ACPICA internal functions. When
concurrent tasks execute ACPI device probing or table lookups across multiple
CPUs, they both invoke `acpi_ut_trace_ptr()` and update `acpi_gbl_nesting_level`
concurrently without mutual exclusion locks.
### Final Classification
**BENIGN**
### Reasoning
`acpi_gbl_nesting_level` is purely a diagnostic/debug counter maintained by
ACPICA to track procedure call nesting depth and update the statistic
`acpi_gbl_deepest_nesting`.
In the Linux kernel driver build (`#ifndef ACPI_APPLICATION`),
`acpi_gbl_nesting_level` is not even included in standard debug printouts (it is
only printed in userland utilities like `acpi_exec` / `iASL`). The counter is
completely decoupled from kernel logic, control flow, locking, memory
management, or hardware interactions. Concurrent lossy updates or torn reads on
`acpi_gbl_nesting_level` have zero effect on functional system behavior or
correctness.
### Recommended Annotations
To suppress KCSAN reports on ACPICA debug tracing counters:
- Wrap updates in `data_race()` macro (e.g.
`data_race(acpi_gbl_nesting_level++)` and
`data_race(acpi_gbl_nesting_level--)`).]
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