Commit 7c5d8fa6 authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

task_work: Decouple TIF_NOTIFY_SIGNAL and task_work 



There are a small handful of reasons besides pending signals that the
kernel might want to break out of interruptible sleeps.  The flag
TIF_NOTIFY_SIGNAL and the helpers that set and clear TIF_NOTIFY_SIGNAL
provide that the infrastructure for breaking out of interruptible
sleeps and entering the return to user space slow path for those
cases.

Expand tracehook_notify_signal inline in it's callers and remove it,
which makes clear that TIF_NOTIFY_SIGNAL and task_work are separate
concepts.

Update the comment on set_notify_signal to more accurately describe
it's purpose.

Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20220309162454.123006-9-ebiederm@xmission.com


Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent 8ba62d37

fs/io-wq.c

+3 −1
Original line number Diff line number Diff line
@@ -515,7 +515,9 @@ static bool io_flush_signals(void) 
{

	if (unlikely(test_thread_flag(TIF_NOTIFY_SIGNAL))) {

		__set_current_state(TASK_RUNNING);

		tracehook_notify_signal();

		clear_notify_signal();

		if (task_work_pending(current))

			task_work_run();

		return true;

	}

	return false;

fs/io_uring.c

+3 −1
Original line number Diff line number Diff line
@@ -2592,7 +2592,9 @@ static inline bool io_run_task_work(void) 
{

	if (test_thread_flag(TIF_NOTIFY_SIGNAL) || task_work_pending(current)) {

		__set_current_state(TASK_RUNNING);

		tracehook_notify_signal();

		clear_notify_signal();

		if (task_work_pending(current))

			task_work_run();

		return true;

	}

include/linux/tracehook.h

+2 −13
Original line number Diff line number Diff line
@@ -113,19 +113,8 @@ static inline void clear_notify_signal(void) 
}



/*

 * called by exit_to_user_mode_loop() if ti_work & _TIF_NOTIFY_SIGNAL. This

 * is currently used by TWA_SIGNAL based task_work, which requires breaking

 * wait loops to ensure that task_work is noticed and run.

 */

static inline void tracehook_notify_signal(void)

{

	clear_notify_signal();

	if (task_work_pending(current))

		task_work_run();

}



/*

 * Called when we have work to process from exit_to_user_mode_loop()

 * Called to break out of interruptible wait loops, and enter the

 * exit_to_user_mode_loop().

 */

static inline void set_notify_signal(struct task_struct *task)

{

kernel/entry/kvm.c

+5 −2
Original line number Diff line number Diff line
@@ -8,8 +8,11 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work) 
	do {

		int ret;



		if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))

			tracehook_notify_signal();

		if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {

			clear_notify_signal();

			if (task_work_pending(current))

				task_work_run();

		}



		if (ti_work & _TIF_SIGPENDING) {

			kvm_handle_signal_exit(vcpu);