Kernel/linux
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2025-01-01 10:43:43 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

dump_stack: avoid the livelock of the dump_lock

Browse Source 
In the current code, we use the atomic_cmpxchg() to serialize the output
of the dump_stack(), but this implementation suffers the thundering herd
problem.  We have observed such kind of livelock on a Marvell cn96xx
board(24 cpus) when heavily using the dump_stack() in a kprobe handler.
Actually we can let the competitors to wait for the releasing of the
lock before jumping to atomic_cmpxchg().  This will definitely mitigate
the thundering herd problem.  Thanks Linus for the suggestion.

[akpm@linux-foundation.org: fix comment]
Link: http://lkml.kernel.org/r/20191030031637.6025-1-haokexin@gmail.com
Fixes: b58d977432 ("dump_stack: serialize the output from dump_stack()")
Signed-off-by: Kevin Hao <haokexin@gmail.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kevin Hao 2019-11-05 21:16:57 -08:00 committed by Linus Torvalds
parent a31631302a
commit 5cbf2fff3b
1 changed files with 6 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
lib/dump_stack.c
View File

@ -106,7 +106,12 @@ asmlinkage __visible void dump_stack(void)
was_locked = 1; was_locked = 1;
} else { } else {
local_irq_restore(flags); local_irq_restore(flags);
cpu_relax(); /*
* Wait for the lock to release before jumping to
* atomic_cmpxchg() in order to mitigate the thundering herd
* problem.
*/
do { cpu_relax(); } while (atomic_read(&dump_lock) != -1);
goto retry; goto retry;
} }