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Merge tag 'core-entry-notify-signal' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into tif-task_work.arch

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Core changes to support TASK_NOTIFY_SIGNAL

* tag 'core-entry-notify-signal' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  task_work: Use TIF_NOTIFY_SIGNAL if available
  entry: Add support for TIF_NOTIFY_SIGNAL
  signal: Add task_sigpending() helper
This commit is contained in:
Jens Axboe
2020-11-09 07:19:32 -07:00
parent f8394f232b 114518eb64
commit 29701d69b9
10 changed files with 118 additions and 30 deletions
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41
kernel/task_work.c
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@@ -5,6 +5,34 @@
static struct callback_head work_exited; /* all we need is ->next == NULL */
/*
* TWA_SIGNAL signaling - use TIF_NOTIFY_SIGNAL, if available, as it's faster
* than TIF_SIGPENDING as there's no dependency on ->sighand. The latter is
* shared for threads, and can cause contention on sighand->lock. Even for
* the non-threaded case TIF_NOTIFY_SIGNAL is more efficient, as no locking
* or IRQ disabling is involved for notification (or running) purposes.
*/
static void task_work_notify_signal(struct task_struct *task)
{
#if defined(TIF_NOTIFY_SIGNAL)
set_notify_signal(task);
#else
unsigned long flags;
/*
* Only grab the sighand lock if we don't already have some
* task_work pending. This pairs with the smp_store_mb()
* in get_signal(), see comment there.
*/
if (!(READ_ONCE(task->jobctl) & JOBCTL_TASK_WORK) &&
lock_task_sighand(task, &flags)) {
task->jobctl |= JOBCTL_TASK_WORK;
signal_wake_up(task, 0);
unlock_task_sighand(task, &flags);
}
#endif
}
/**
* task_work_add - ask the @task to execute @work->func()
* @task: the task which should run the callback
@@ -33,7 +61,6 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
enum task_work_notify_mode notify)
{
struct callback_head *head;
unsigned long flags;
do {
head = READ_ONCE(task->task_works);
@@ -49,17 +76,7 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
set_notify_resume(task);
break;
case TWA_SIGNAL:
/*
* Only grab the sighand lock if we don't already have some
* task_work pending. This pairs with the smp_store_mb()
* in get_signal(), see comment there.
*/
if (!(READ_ONCE(task->jobctl) & JOBCTL_TASK_WORK) &&
lock_task_sighand(task, &flags)) {
task->jobctl |= JOBCTL_TASK_WORK;
signal_wake_up(task, 0);
unlock_task_sighand(task, &flags);
}
task_work_notify_signal(task);
break;
default:
WARN_ON_ONCE(1);