From 03941ccfda161c2680147fa5ab92aead2a79cac1 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 9 Oct 2020 16:01:33 -0600 Subject: task_work: remove legacy TWA_SIGNAL path All archs now support TIF_NOTIFY_SIGNAL. Signed-off-by: Jens Axboe --- kernel/task_work.c | 30 +----------------------------- 1 file changed, 1 insertion(+), 29 deletions(-) (limited to 'kernel') diff --git a/kernel/task_work.c b/kernel/task_work.c index 15b087286bea..9cde961875c0 100644 --- a/kernel/task_work.c +++ b/kernel/task_work.c @@ -5,34 +5,6 @@ static struct callback_head work_exited; /* all we need is ->next == NULL */ -/* - * TWA_SIGNAL signaling - use TIF_NOTIFY_SIGNAL, if available, as it's faster - * than TIF_SIGPENDING as there's no dependency on ->sighand. The latter is - * shared for threads, and can cause contention on sighand->lock. Even for - * the non-threaded case TIF_NOTIFY_SIGNAL is more efficient, as no locking - * or IRQ disabling is involved for notification (or running) purposes. - */ -static void task_work_notify_signal(struct task_struct *task) -{ -#if defined(TIF_NOTIFY_SIGNAL) - set_notify_signal(task); -#else - unsigned long flags; - - /* - * Only grab the sighand lock if we don't already have some - * task_work pending. This pairs with the smp_store_mb() - * in get_signal(), see comment there. - */ - if (!(READ_ONCE(task->jobctl) & JOBCTL_TASK_WORK) && - lock_task_sighand(task, &flags)) { - task->jobctl |= JOBCTL_TASK_WORK; - signal_wake_up(task, 0); - unlock_task_sighand(task, &flags); - } -#endif -} - /** * task_work_add - ask the @task to execute @work->func() * @task: the task which should run the callback @@ -76,7 +48,7 @@ int task_work_add(struct task_struct *task, struct callback_head *work, set_notify_resume(task); break; case TWA_SIGNAL: - task_work_notify_signal(task); + set_notify_signal(task); break; default: WARN_ON_ONCE(1); -- cgit v1.2.3 From 98b89b649fce39dacb9dc036d6d0fdb8caff73f7 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 9 Oct 2020 16:03:01 -0600 Subject: signal: kill JOBCTL_TASK_WORK It's no longer used, get rid of it. Signed-off-by: Jens Axboe --- include/linux/sched/jobctl.h | 4 +--- kernel/signal.c | 20 -------------------- 2 files changed, 1 insertion(+), 23 deletions(-) (limited to 'kernel') diff --git a/include/linux/sched/jobctl.h b/include/linux/sched/jobctl.h index d2b4204ba4d3..fa067de9f1a9 100644 --- a/include/linux/sched/jobctl.h +++ b/include/linux/sched/jobctl.h @@ -19,7 +19,6 @@ struct task_struct; #define JOBCTL_TRAPPING_BIT 21 /* switching to TRACED */ #define JOBCTL_LISTENING_BIT 22 /* ptracer is listening for events */ #define JOBCTL_TRAP_FREEZE_BIT 23 /* trap for cgroup freezer */ -#define JOBCTL_TASK_WORK_BIT 24 /* set by TWA_SIGNAL */ #define JOBCTL_STOP_DEQUEUED (1UL << JOBCTL_STOP_DEQUEUED_BIT) #define JOBCTL_STOP_PENDING (1UL << JOBCTL_STOP_PENDING_BIT) @@ -29,10 +28,9 @@ struct task_struct; #define JOBCTL_TRAPPING (1UL << JOBCTL_TRAPPING_BIT) #define JOBCTL_LISTENING (1UL << JOBCTL_LISTENING_BIT) #define JOBCTL_TRAP_FREEZE (1UL << JOBCTL_TRAP_FREEZE_BIT) -#define JOBCTL_TASK_WORK (1UL << JOBCTL_TASK_WORK_BIT) #define JOBCTL_TRAP_MASK (JOBCTL_TRAP_STOP | JOBCTL_TRAP_NOTIFY) -#define JOBCTL_PENDING_MASK (JOBCTL_STOP_PENDING | JOBCTL_TRAP_MASK | JOBCTL_TASK_WORK) +#define JOBCTL_PENDING_MASK (JOBCTL_STOP_PENDING | JOBCTL_TRAP_MASK) extern bool task_set_jobctl_pending(struct task_struct *task, unsigned long mask); extern void task_clear_jobctl_trapping(struct task_struct *task); diff --git a/kernel/signal.c b/kernel/signal.c index 923230ff6cfc..cf8b057ca2ac 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2556,26 +2556,6 @@ bool get_signal(struct ksignal *ksig) relock: spin_lock_irq(&sighand->siglock); - /* - * Make sure we can safely read ->jobctl() in task_work add. As Oleg - * states: - * - * It pairs with mb (implied by cmpxchg) before READ_ONCE. So we - * roughly have - * - * task_work_add: get_signal: - * STORE(task->task_works, new_work); STORE(task->jobctl); - * mb(); mb(); - * LOAD(task->jobctl); LOAD(task->task_works); - * - * and we can rely on STORE-MB-LOAD [ in task_work_add]. - */ - smp_store_mb(current->jobctl, current->jobctl & ~JOBCTL_TASK_WORK); - if (unlikely(current->task_works)) { - spin_unlock_irq(&sighand->siglock); - task_work_run(); - goto relock; - } /* * Every stopped thread goes here after wakeup. Check to see if -- cgit v1.2.3 From e296dc4996b8094ccde45d19090d804c4103513e Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 9 Oct 2020 16:04:39 -0600 Subject: kernel: remove checking for TIF_NOTIFY_SIGNAL It's available everywhere now, no need to check or add dummy defines. Signed-off-by: Jens Axboe --- include/linux/entry-common.h | 4 ---- include/linux/sched/signal.h | 2 -- include/linux/tracehook.h | 4 ---- kernel/signal.c | 2 -- 4 files changed, 12 deletions(-) (limited to 'kernel') diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h index b9711e813ec2..abec3a5ae799 100644 --- a/include/linux/entry-common.h +++ b/include/linux/entry-common.h @@ -37,10 +37,6 @@ # define _TIF_UPROBE (0) #endif -#ifndef _TIF_NOTIFY_SIGNAL -# define _TIF_NOTIFY_SIGNAL (0) -#endif - /* * TIF flags handled in syscall_enter_from_user_mode() */ diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h index bd5afa076189..24b7b862e043 100644 --- a/include/linux/sched/signal.h +++ b/include/linux/sched/signal.h @@ -360,7 +360,6 @@ static inline int task_sigpending(struct task_struct *p) static inline int signal_pending(struct task_struct *p) { -#if defined(TIF_NOTIFY_SIGNAL) /* * TIF_NOTIFY_SIGNAL isn't really a signal, but it requires the same * behavior in terms of ensuring that we break out of wait loops @@ -368,7 +367,6 @@ static inline int signal_pending(struct task_struct *p) */ if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL))) return 1; -#endif return task_sigpending(p); } diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h index f7d82e4fafd6..ee9ab7dbc8c3 100644 --- a/include/linux/tracehook.h +++ b/include/linux/tracehook.h @@ -205,12 +205,10 @@ static inline void tracehook_notify_resume(struct pt_regs *regs) */ static inline void tracehook_notify_signal(void) { -#if defined(TIF_NOTIFY_SIGNAL) clear_thread_flag(TIF_NOTIFY_SIGNAL); smp_mb__after_atomic(); if (current->task_works) task_work_run(); -#endif } /* @@ -218,11 +216,9 @@ static inline void tracehook_notify_signal(void) */ static inline void set_notify_signal(struct task_struct *task) { -#if defined(TIF_NOTIFY_SIGNAL) if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_SIGNAL) && !wake_up_state(task, TASK_INTERRUPTIBLE)) kick_process(task); -#endif } #endif /* */ diff --git a/kernel/signal.c b/kernel/signal.c index cf8b057ca2ac..ccd530509201 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2535,14 +2535,12 @@ bool get_signal(struct ksignal *ksig) * that the arch handlers don't all have to do it. If we get here * without TIF_SIGPENDING, just exit after running signal work. */ -#ifdef TIF_NOTIFY_SIGNAL if (!IS_ENABLED(CONFIG_GENERIC_ENTRY)) { if (test_thread_flag(TIF_NOTIFY_SIGNAL)) tracehook_notify_signal(); if (!task_sigpending(current)) return false; } -#endif if (unlikely(uprobe_deny_signal())) return false; -- cgit v1.2.3