[PATCH] convert sighand_cache to use SLAB_DESTROY_BY_RCU
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>
diff --git a/kernel/signal.c b/kernel/signal.c
index dc8f91b..b0b1ca9 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -330,7 +330,7 @@
/* Ok, we're done with the signal handlers */
tsk->sighand = NULL;
if (atomic_dec_and_test(&sighand->count))
- sighand_free(sighand);
+ kmem_cache_free(sighand_cachep, sighand);
}
void exit_sighand(struct task_struct *tsk)