From: Oleg Nesterov <oleg@redhat.com>
Date: Thu, 16 Apr 2015 19:47:32 +0000 (-0700)
Subject: ptrace: ptrace_detach() can no longer race with SIGKILL
X-Git-Tag: omap-for-v4.1/fixes-rc1~115^2~44
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=64a4096c5cdab377b6e1f44008ee8b2636db579d;p=pandora-kernel.git

ptrace: ptrace_detach() can no longer race with SIGKILL

ptrace_detach() re-checks ->ptrace under tasklist lock and calls
release_task() if __ptrace_detach() returns true.  This was needed because
the __TASK_TRACED tracee could be killed/untraced, and it could even pass
exit_notify() before we take tasklist_lock.

But this is no longer possible after 9899d11f6544 "ptrace: ensure
arch_ptrace/ptrace_request can never race with SIGKILL".  We can turn
these checks into WARN_ON() and remove release_task().

While at it, document the setting of child->exit_code.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Pavel Labath <labath@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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