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workqueue: debug flushing deadlocks with lockdep

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In the following scenario:

code path 1:
  my_function() -> lock(L1); ...; flush_workqueue(); ...

code path 2:
  run_workqueue() -> my_work() -> ...; lock(L1); ...

you can get a deadlock when my_work() is queued or running
but my_function() has acquired L1 already.

This patch adds a pseudo-lock to each workqueue to make lockdep
warn about this scenario.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Berg
2007-10-18 23:39:55 -07:00
committed by Linus Torvalds
parent cf7b708c8d
commit 4e6045f134
4 changed files with 88 additions and 7 deletions
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2
kernel/lockdep.c
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@@ -1521,7 +1521,7 @@ cache_hit:
}
static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
struct held_lock *hlock, int chain_head, u64 chain_key)
struct held_lock *hlock, int chain_head, u64 chain_key)
{
/*
* Trylock needs to maintain the stack of held locks, but it