======================================================
WARNING: possible circular locking dependency detected
4.14.123+ #1 Not tainted
------------------------------------------------------
syz-executor.1/4037 is trying to acquire lock:
 (&cpuctx_mutex/1){+.+.}, at: [<00000000c738284e>] mutex_lock_double kernel/events/core.c:9909 [inline]
 (&cpuctx_mutex/1){+.+.}, at: [<00000000c738284e>] __perf_event_ctx_lock_double kernel/events/core.c:9968 [inline]
 (&cpuctx_mutex/1){+.+.}, at: [<00000000c738284e>] SYSC_perf_event_open kernel/events/core.c:10233 [inline]
 (&cpuctx_mutex/1){+.+.}, at: [<00000000c738284e>] SyS_perf_event_open+0x12b2/0x2530 kernel/events/core.c:9988

but task is already holding lock:
 (&cpuctx_mutex){+.+.}, at: [<00000000f025e855>] mutex_lock_double kernel/events/core.c:9908 [inline]
 (&cpuctx_mutex){+.+.}, at: [<00000000f025e855>] __perf_event_ctx_lock_double kernel/events/core.c:9968 [inline]
 (&cpuctx_mutex){+.+.}, at: [<00000000f025e855>] SYSC_perf_event_open kernel/events/core.c:10233 [inline]
 (&cpuctx_mutex){+.+.}, at: [<00000000f025e855>] SyS_perf_event_open+0x12a5/0x2530 kernel/events/core.c:9988

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&cpuctx_mutex){+.+.}:

-> #1 (pmus_lock){+.+.}:

-> #0 (&cpuctx_mutex/1){+.+.}:

other info that might help us debug this:

Chain exists of:
  &cpuctx_mutex/1 --> pmus_lock --> &cpuctx_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&cpuctx_mutex);
                               lock(pmus_lock);
                               lock(&cpuctx_mutex);
  lock(&cpuctx_mutex/1);

 *** DEADLOCK ***

1 lock held by syz-executor.1/4037:
 #0:  (&cpuctx_mutex){+.+.}, at: [<00000000f025e855>] mutex_lock_double kernel/events/core.c:9908 [inline]
 #0:  (&cpuctx_mutex){+.+.}, at: [<00000000f025e855>] __perf_event_ctx_lock_double kernel/events/core.c:9968 [inline]
 #0:  (&cpuctx_mutex){+.+.}, at: [<00000000f025e855>] SYSC_perf_event_open kernel/events/core.c:10233 [inline]
 #0:  (&cpuctx_mutex){+.+.}, at: [<00000000f025e855>] SyS_perf_event_open+0x12a5/0x2530 kernel/events/core.c:9988

stack backtrace:
CPU: 1 PID: 4037 Comm: syz-executor.1 Not tainted 4.14.123+ #1
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xb9/0x10e lib/dump_stack.c:53
 print_circular_bug.isra.0.cold+0x2dc/0x425 kernel/locking/lockdep.c:1258