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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
  1. fs/io-wq.c +3 −1
  2. fs/io_uring.c +3 −1
  3. include/linux/tracehook.h +2 −13
  4. 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 if (unlikely(test_thread_flag(TIF_NOTIFY_SIGNAL))) {516 if (unlikely(test_thread_flag(TIF_NOTIFY_SIGNAL))) {
517 __set_current_state(TASK_RUNNING);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 return true;521 return true;
520 }522 }
521 return false;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 if (test_thread_flag(TIF_NOTIFY_SIGNAL) || task_work_pending(current)) {2593 if (test_thread_flag(TIF_NOTIFY_SIGNAL) || task_work_pending(current)) {
2594 __set_current_state(TASK_RUNNING);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 return true;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. This116 * Called to break out of interruptible wait loops, and enter the
117 * is currently used by TWA_SIGNAL based task_work, which requires breaking117 * exit_to_user_mode_loop().
118 * wait loops to ensure that task_work is noticed and run.
119 */
120static 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()
129 */118 */
130static inline void set_notify_signal(struct task_struct *task)119static 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 do {8 do {
9 int ret;9 int ret;
10 10
11 if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))11 if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
12 tracehook_notify_signal();12 clear_notify_signal();
13 if (task_work_pending(current))
14 task_work_run();
15 }
13 16
14 if (ti_work & _TIF_SIGPENDING) {17 if (ti_work & _TIF_SIGPENDING) {
15 kvm_handle_signal_exit(vcpu);18 kvm_handle_signal_exit(vcpu);