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authorOleg Nesterov <oleg@redhat.com>2012-05-11 10:59:07 +1000
committerAl Viro <viro@zeniv.linux.org.uk>2012-05-23 22:09:21 -0400
commite73f8959af0439d114847eab5a8a5ce48f1217c4 (patch)
tree47f056093590a5e5552e3a75f163e1f798063bda /kernel/exit.c
parent62366c88b29c5a32e1531142092f98eaf49b1103 (diff)
task_work_add: generic process-context callbacks
Provide a simple mechanism that allows running code in the (nonatomic) context of the arbitrary task. The caller does task_work_add(task, task_work) and this task executes task_work->func() either from do_notify_resume() or from do_exit(). The callback can rely on PF_EXITING to detect the latter case. "struct task_work" can be embedded in another struct, still it has "void *data" to handle the most common/simple case. This allows us to kill the ->replacement_session_keyring hack, and potentially this can have more users. Performance-wise, this adds 2 "unlikely(!hlist_empty())" checks into tracehook_notify_resume() and do_exit(). But at the same time we can remove the "replacement_session_keyring != NULL" checks from arch/*/signal.c and exit_creds(). Note: task_work_add/task_work_run abuses ->pi_lock. This is only because this lock is already used by lookup_pi_state() to synchronize with do_exit() setting PF_EXITING. Fortunately the scope of this lock in task_work.c is really tiny, and the code is unlikely anyway. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: David Howells <dhowells@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Richard Kuo <rkuo@codeaurora.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Alexander Gordeev <agordeev@redhat.com> Cc: Chris Zankel <chris@zankel.net> Cc: David Smith <dsmith@redhat.com> Cc: "Frank Ch. Eigler" <fche@redhat.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Larry Woodman <lwoodman@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Tejun Heo <tj@kernel.org> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'kernel/exit.c')
-rw-r--r--kernel/exit.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 910a0716e17..3d93325e0b1 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -946,11 +946,14 @@ void do_exit(long code)
exit_signals(tsk); /* sets PF_EXITING */
/*
* tsk->flags are checked in the futex code to protect against
- * an exiting task cleaning up the robust pi futexes.
+ * an exiting task cleaning up the robust pi futexes, and in
+ * task_work_add() to avoid the race with exit_task_work().
*/
smp_mb();
raw_spin_unlock_wait(&tsk->pi_lock);
+ exit_task_work(tsk);
+
exit_irq_thread();
if (unlikely(in_atomic()))