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.

Eric W. Biederman committed 4 years ago

Commit 7c5d8fa1 parent 8ba62d34 files · +13 −17Browse files

Unified · Split

4 files

fs/io-wq.c +3 −1
fs/io_uring.c +3 −1
include/linux/tracehook.h +2 −13
kernel/entry/kvm.c +5 −2

fs/io-wq.c+3−1

@@ -515,7 +515,9 @@ static bool io_flush_signals(void) · 514 unmodified lines
515	515	{
516	516	if (unlikely(test_thread_flag(TIF_NOTIFY_SIGNAL))) {
517	517	__set_current_state(TASK_RUNNING);
518		− tracehook_notify_signal();
	518	+ clear_notify_signal();
	519	+ if (task_work_pending(current))
	520	+ task_work_run();
519	521	return true;
520	522	}
521	523	return false;

fs/io_uring.c+3−1

@@ -2592,7 +2592,9 @@ static inline bool io_run_task_work(void) · 2591 unmodified lines
2592	2592	{
2593	2593	if (test_thread_flag(TIF_NOTIFY_SIGNAL) \|\| task_work_pending(current)) {
2594	2594	__set_current_state(TASK_RUNNING);
2595		− tracehook_notify_signal();
	2595	+ clear_notify_signal();
	2596	+ if (task_work_pending(current))
	2597	+ task_work_run();
2596	2598	return true;
2597	2599	}
2598	2600

include/linux/tracehook.h+2−13

@@ -113,19 +113,8 @@ static inline void clear_notify_signal(void) · 112 unmodified lines
113	113	}
114	114
115	115	/*
116		− * called by exit_to_user_mode_loop() if ti_work & _TIF_NOTIFY_SIGNAL. This
117		− * is currently used by TWA_SIGNAL based task_work, which requires breaking
118		− * wait loops to ensure that task_work is noticed and run.
119		− */
120		−static inline void tracehook_notify_signal(void)
121		−{
122		− clear_notify_signal();
123		− if (task_work_pending(current))
124		− task_work_run();
125		−}
126		−
127		−/*
128		− * Called when we have work to process from exit_to_user_mode_loop()
	116	+ * Called to break out of interruptible wait loops, and enter the
	117	+ * exit_to_user_mode_loop().
129	118	*/
130	119	static inline void set_notify_signal(struct task_struct *task)
131	120	{

kernel/entry/kvm.c+5−2

@@ -8,8 +8,11 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work) · 7 unmodified lines
8	8	do {
9	9	int ret;
10	10
11		− if (ti_work & (_TIF_SIGPENDING \| _TIF_NOTIFY_SIGNAL))
12		− tracehook_notify_signal();
	11	+ if (ti_work & (_TIF_SIGPENDING \| _TIF_NOTIFY_SIGNAL)) {
	12	+ clear_notify_signal();
	13	+ if (task_work_pending(current))
	14	+ task_work_run();
	15	+ }
13	16
14	17	if (ti_work & _TIF_SIGPENDING) {
15	18	kvm_handle_signal_exit(vcpu);