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authorJens Axboe <axboe@kernel.dk>2020-11-09 07:19:32 -0700
committerJens Axboe <axboe@kernel.dk>2020-11-09 07:19:32 -0700
commit29701d69b98d0a132abd63fe2e51125f478fbc53 (patch)
tree0650d3905c76124eb8c29d17c8434b5bb8954fe2 /kernel/task_work.c
parentf8394f232b1eab649ce2df5c5f15b0e528c92091 (diff)
parent114518eb6430b832d2f9f5a008043b913ccf0e24 (diff)
Merge tag 'core-entry-notify-signal' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into tif-task_work.arch
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
Diffstat (limited to 'kernel/task_work.c')
-rw-r--r--kernel/task_work.c41
1 files changed, 29 insertions, 12 deletions
diff --git a/kernel/task_work.c b/kernel/task_work.c
index 8d6e1217c451..15b087286bea 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -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);