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[PATCH] convert sighand_cache to use SLAB_DESTROY_BY_RCU

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This patch borrows a clever Hugh's 'struct anon_vma' trick.

Without tasklist_lock held we can't trust task->sighand until we locked it
and re-checked that it is still the same.

But this means we don't need to defer 'kmem_cache_free(sighand)'.  We can
return the memory to slab immediately, all we need is to be sure that
sighand->siglock can't dissapear inside rcu protected section.

To do so we need to initialize ->siglock inside ctor function,
SLAB_DESTROY_BY_RCU does the rest.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Oleg Nesterov
2006-03-28 16:11:12 -08:00
committed by Linus Torvalds
parent 1f09f9749c
commit aa1757f90b
4 changed files with 13 additions and 21 deletions
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3
fs/exec.c
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@@ -768,7 +768,6 @@ no_thread_group:
/*
* Move our state over to newsighand and switch it in.
*/
spin_lock_init(&newsighand->siglock);
atomic_set(&newsighand->count, 1);
memcpy(newsighand->action, oldsighand->action,
sizeof(newsighand->action));
@@ -785,7 +784,7 @@ no_thread_group:
write_unlock_irq(&tasklist_lock);
if (atomic_dec_and_test(&oldsighand->count))
sighand_free(oldsighand);
kmem_cache_free(sighand_cachep, oldsighand);
}
BUG_ON(!thread_group_leader(current));