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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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8
include/linux/sched.h
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@@ -355,16 +355,8 @@ struct sighand_struct {
atomic_t count;
struct k_sigaction action[_NSIG];
spinlock_t siglock;
struct rcu_head rcu;
};
extern void sighand_free_cb(struct rcu_head *rhp);
static inline void sighand_free(struct sighand_struct *sp)
{
call_rcu(&sp->rcu, sighand_free_cb);
}
/*
* NOTE! "signal_struct" does not have it's own
* locking, because a shared signal_struct always