syzbot


WARNING: suspicious RCU usage in rmap_walk_file

Status: fixed on 2021/11/10 00:50
Subsystems: mm
[Documentation on labels]
Fix commit: 3066820034b5 rcu: Reject RCU_LOCKDEP_WARN() false positives
First crash: 1105d, last: 1105d

Sample crash report:
=============================
WARNING: suspicious RCU usage
5.13.0-rc1-syzkaller #0 Not tainted
-----------------------------
kernel/sched/core.c:8304 Illegal context switch in RCU-sched read-side critical section!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 0
1 lock held by kswapd1/2182:
 #0: ffffffff8c093fe0 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x0/0x30 mm/page_alloc.c:5396

stack backtrace:
CPU: 3 PID: 2182 Comm: kswapd1 Not tainted 5.13.0-rc1-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 lib/dump_stack.c:120
 ___might_sleep+0x266/0x2c0 kernel/sched/core.c:8304
 down_read+0x73/0x440 kernel/locking/rwsem.c:1352
 i_mmap_lock_read include/linux/fs.h:509 [inline]
 rmap_walk_file+0x6d1/0xca0 mm/rmap.c:1926
 rmap_walk+0x105/0x190 mm/rmap.c:1954
 page_referenced+0x3c6/0x4b0 mm/rmap.c:895
 page_check_references mm/vmscan.c:1187 [inline]
 shrink_page_list+0x2803/0x6060 mm/vmscan.c:1416
 shrink_inactive_list+0x347/0xca0 mm/vmscan.c:2145
 shrink_list mm/vmscan.c:2367 [inline]
 shrink_lruvec+0x7f9/0x14f0 mm/vmscan.c:2662
 shrink_node_memcgs mm/vmscan.c:2850 [inline]
 shrink_node+0x868/0x1de0 mm/vmscan.c:2967
 kswapd_shrink_node mm/vmscan.c:3710 [inline]
 balance_pgdat+0x745/0x1270 mm/vmscan.c:3868
 kswapd+0x5b6/0xdb0 mm/vmscan.c:4125
 kthread+0x3b1/0x4a0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2021/05/14 00:26 upstream c06a2ba62fc4 ecb594cb .config console log report info ci-qemu-upstream WARNING: suspicious RCU usage in rmap_walk_file
* Struck through repros no longer work on HEAD.