From e73f8959af0439d114847eab5a8a5ce48f1217c4 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 11 May 2012 10:59:07 +1000 Subject: 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 Acked-by: David Howells Cc: Thomas Gleixner Cc: Richard Kuo Cc: Linus Torvalds Cc: Alexander Gordeev Cc: Chris Zankel Cc: David Smith Cc: "Frank Ch. Eigler" Cc: Geert Uytterhoeven Cc: Larry Woodman Cc: Peter Zijlstra Cc: Tejun Heo Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Al Viro --- kernel/fork.c | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel/fork.c') diff --git a/kernel/fork.c b/kernel/fork.c index 05c813dc9ecc..a46db217a589 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1411,6 +1411,7 @@ static struct task_struct *copy_process(unsigned long clone_flags, */ p->group_leader = p; INIT_LIST_HEAD(&p->thread_group); + INIT_HLIST_HEAD(&p->task_works); /* Now that the task is set up, run cgroup callbacks if * necessary. We need to run them before the task is visible -- cgit v1.2.3-58-ga151