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" --- kernel/task_work.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/task_work.c') diff --git a/kernel/task_work.c b/kernel/task_work.c index 1698fbe6f0e1..cc6fccb0e24d 100644 --- a/kernel/task_work.c +++ b/kernel/task_work.c @@ -78,7 +78,7 @@ task_work_cancel_match(struct task_struct *task, struct callback_head *work; unsigned long flags; - if (likely(!task->task_works)) + if (likely(!task_work_pending(task))) return NULL; /* * If cmpxchg() fails we continue without updating pprev. -- cgit v1.2.3 From 03248addadf1a5ef0a03cbcd5ec905b49adb9658 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Wed, 9 Feb 2022 12:20:45 -0600 Subject: resume_user_mode: Move to resume_user_mode.h Move set_notify_resume and tracehook_notify_resume into resume_user_mode.h. While doing that rename tracehook_notify_resume to resume_user_mode_work. Update all of the places that included tracehook.h for these functions to include resume_user_mode.h instead. Update all of the callers of tracehook_notify_resume to call resume_user_mode_work. Reviewed-by: Kees Cook Link: https://lkml.kernel.org/r/20220309162454.123006-12-ebiederm@xmission.com Signed-off-by: "Eric W. Biederman" --- kernel/task_work.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/task_work.c') diff --git a/kernel/task_work.c b/kernel/task_work.c index cc6fccb0e24d..c59e1a49bc40 100644 --- a/kernel/task_work.c +++ b/kernel/task_work.c @@ -1,7 +1,7 @@ // SPDX-License-Identifier: GPL-2.0 #include #include -#include +#include static struct callback_head work_exited; /* all we need is ->next == NULL */ -- 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 --- kernel/task_work.c | 25 +++++++++++++++++++------ 1 file changed, 19 insertions(+), 6 deletions(-) (limited to 'kernel/task_work.c') diff --git a/kernel/task_work.c b/kernel/task_work.c index c59e1a49bc40..dff75bcde151 100644 --- a/kernel/task_work.c +++ b/kernel/task_work.c @@ -12,12 +12,22 @@ static struct callback_head work_exited; /* all we need is ->next == NULL */ * @notify: how to notify the targeted task * * Queue @work for task_work_run() below and notify the @task if @notify - * is @TWA_RESUME or @TWA_SIGNAL. @TWA_SIGNAL works like signals, in that the - * it will interrupt the targeted task and run the task_work. @TWA_RESUME - * work is run only when the task exits the kernel and returns to user mode, - * or before entering guest mode. Fails if the @task is exiting/exited and thus - * it can't process this @work. Otherwise @work->func() will be called when the - * @task goes through one of the aforementioned transitions, or exits. + * is @TWA_RESUME, @TWA_SIGNAL, or @TWA_SIGNAL_NO_IPI. + * + * @TWA_SIGNAL works like signals, in that the it will interrupt the targeted + * task and run the task_work, regardless of whether the task is currently + * running in the kernel or userspace. + * @TWA_SIGNAL_NO_IPI works like @TWA_SIGNAL, except it doesn't send a + * reschedule IPI to force the targeted task to reschedule and run task_work. + * This can be advantageous if there's no strict requirement that the + * task_work be run as soon as possible, just whenever the task enters the + * kernel anyway. + * @TWA_RESUME work is run only when the task exits the kernel and returns to + * user mode, or before entering guest mode. + * + * Fails if the @task is exiting/exited and thus it can't process this @work. + * Otherwise @work->func() will be called when the @task goes through one of + * the aforementioned transitions, or exits. * * If the targeted task is exiting, then an error is returned and the work item * is not queued. It's up to the caller to arrange for an alternative mechanism @@ -53,6 +63,9 @@ int task_work_add(struct task_struct *task, struct callback_head *work, case TWA_SIGNAL: set_notify_signal(task); break; + case TWA_SIGNAL_NO_IPI: + __set_notify_signal(task); + break; default: WARN_ON_ONCE(1); break; -- cgit v1.2.3