From: Tejun Heo <tj@kernel.org>
Date: Thu, 2 Jun 2011 09:14:00 +0000 (+0200)
Subject: ptrace: use bit_waitqueue for TRAPPING instead of wait_chldexit
X-Git-Tag: v3.1-rc1~308^2~31
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=62c124ff3bcdb414af635c2bf822c9e4f2a5abfa;p=pandora-kernel.git

ptrace: use bit_waitqueue for TRAPPING instead of wait_chldexit

ptracer->signal->wait_chldexit was used to wait for TRAPPING; however,
->wait_chldexit was already complicated with waker-side filtering
without adding TRAPPING wait on top of it.  Also, it unnecessarily
made TRAPPING clearing depend on the current ptrace relationship - if
the ptracee is detached, wakeup is lost.

There is no reason to use signal->wait_chldexit here.  We're just
waiting for JOBCTL_TRAPPING bit to clear and given the relatively
infrequent use of ptrace, bit_waitqueue can serve it perfectly.

This patch makes JOBCTL_TRAPPING wait use bit_waitqueue instead of
signal->wait_chldexit.

-v2: Use JOBCTL_*_BIT macros instead of ilog2() as suggested by Linus.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---

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