From: Oleg Nesterov <oleg@tv-sign.ru>
Date: Wed, 29 Mar 2006 00:11:12 +0000 (-0800)
Subject: [PATCH] convert sighand_cache to use SLAB_DESTROY_BY_RCU
X-Git-Tag: v2.6.17-rc1~189
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=aa1757f90bea3f598b6e5d04d922a6a60200f1da;p=pandora-kernel.git

[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>
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