task_work: task_work_add() should not succeed after exit_task_work()
authorOleg Nesterov <oleg@redhat.com>
Sun, 26 Aug 2012 19:12:11 +0000 (21:12 +0200)
committerIngo Molnar <mingo@kernel.org>
Thu, 13 Sep 2012 14:47:34 +0000 (16:47 +0200)
commit9da33de62431c7839f98156720862262272a8380
tree1a05e4bab566cf0aeba5890e536387c0859012ac
parentac3d0da8f3290b3d394cdb7f50604424a7cd6092
task_work: task_work_add() should not succeed after exit_task_work()

ed3e694d "move exit_task_work() past exit_files() et.al" destroyed
the add/exit synchronization we had, the caller itself should ensure
task_work_add() can't race with the exiting task.

However, this is not convenient/simple, and the only user which tries
to do this is buggy (see the next patch). Unless the task is current,
there is simply no way to do this in general.

Change exit_task_work()->task_work_run() to use the dummy "work_exited"
entry to let task_work_add() know it should fail.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20120826191211.GA4228@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
include/linux/task_work.h
kernel/task_work.c