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| author | Oleg Nesterov <oleg@redhat.com> | 2012-05-11 10:59:07 +1000 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2012-05-23 22:09:21 -0400 |
| commit | e73f8959af0439d114847eab5a8a5ce48f1217c4 (patch) | |
| tree | 47f056093590a5e5552e3a75f163e1f798063bda /include/linux/tracehook.h | |
| parent | 62366c88b29c5a32e1531142092f98eaf49b1103 (diff) | |
| download | lwn-e73f8959af0439d114847eab5a8a5ce48f1217c4.tar.gz lwn-e73f8959af0439d114847eab5a8a5ce48f1217c4.zip | |
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 'include/linux/tracehook.h')
| -rw-r--r-- | include/linux/tracehook.h | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h index b9ca903bb553..b2dd0917ca0d 100644 --- a/include/linux/tracehook.h +++ b/include/linux/tracehook.h @@ -49,6 +49,7 @@ #include <linux/sched.h> #include <linux/ptrace.h> #include <linux/security.h> +#include <linux/task_work.h> struct linux_binprm; /* @@ -164,8 +165,10 @@ static inline void tracehook_signal_handler(int sig, siginfo_t *info, */ static inline void set_notify_resume(struct task_struct *task) { +#ifdef TIF_NOTIFY_RESUME if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME)) kick_process(task); +#endif } /** @@ -185,6 +188,14 @@ static inline void tracehook_notify_resume(struct pt_regs *regs) { if (current->replacement_session_keyring) key_replace_session_keyring(); + /* + * The caller just cleared TIF_NOTIFY_RESUME. This barrier + * pairs with task_work_add()->set_notify_resume() after + * hlist_add_head(task->task_works); + */ + smp_mb__after_clear_bit(); + if (unlikely(!hlist_empty(¤t->task_works))) + task_work_run(); } #endif /* <linux/tracehook.h> */ |