From 7f62d40d9cb50fd146fe8ff071f98fa3c1855083 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Wed, 9 Feb 2022 08:52:41 -0600 Subject: task_work: Introduce task_work_pending Wrap the test of task->task_works in a helper function to make it clear what is being tested. All of the other readers of task->task_work use READ_ONCE and this is even necessary on current as other processes can update task->task_work. So for consistency I have added READ_ONCE into task_work_pending. Reviewed-by: Kees Cook Link: https://lkml.kernel.org/r/20220309162454.123006-7-ebiederm@xmission.com Signed-off-by: "Eric W. Biederman" --- include/linux/task_work.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux/task_work.h') diff --git a/include/linux/task_work.h b/include/linux/task_work.h index 5b8a93f288bb..897494b597ba 100644 --- a/include/linux/task_work.h +++ b/include/linux/task_work.h @@ -19,6 +19,11 @@ enum task_work_notify_mode { TWA_SIGNAL, }; +static inline bool task_work_pending(struct task_struct *task) +{ + return READ_ONCE(task->task_works); +} + int task_work_add(struct task_struct *task, struct callback_head *twork, enum task_work_notify_mode mode); -- cgit v1.2.3 From e788be95a57a9bebe446878ce9bf2750f6fe4974 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 28 Apr 2022 17:25:16 -0600 Subject: task_work: allow TWA_SIGNAL without a rescheduling IPI Some use cases don't always need an IPI when sending a TWA_SIGNAL notification. Add TWA_SIGNAL_NO_IPI, which is just like TWA_SIGNAL, except it doesn't send an IPI to the target task. It merely sets TIF_NOTIFY_SIGNAL and wakes up the task. This can be useful in avoiding a forceful transition to the kernel if the task is running in userspace. Depending on the task_work in question, it may be quite fine waiting for the next reschedule or kernel enter anyway, or the use case may even have other mechanisms for hinting to the task that a transition may be useful. This can drive more cooperative scheduling of task_work. Reviewed-by: Pavel Begunkov Link: https://lore.kernel.org/r/821f42b6-7d91-8074-8212-d34998097de4@kernel.dk Signed-off-by: Jens Axboe --- include/linux/task_work.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/task_work.h') diff --git a/include/linux/task_work.h b/include/linux/task_work.h index 897494b597ba..795ef5a68429 100644 --- a/include/linux/task_work.h +++ b/include/linux/task_work.h @@ -17,6 +17,7 @@ enum task_work_notify_mode { TWA_NONE, TWA_RESUME, TWA_SIGNAL, + TWA_SIGNAL_NO_IPI, }; static inline bool task_work_pending(struct task_struct *task) -- cgit v1.2.3