Merge branch 'core/urgent' into core/entry

Pick up the entry fix before further modifications.

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index be0d7d4..ea794a0 100644 (file)
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -804,11 +804,11 @@ static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
  * want to handle. Thus you cannot kill init even with a SIGKILL even by
  * mistake.
  */
-void arch_do_signal(struct pt_regs *regs)
+void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal)
 {
        struct ksignal ksig;
 
-       if (get_signal(&ksig)) {
+       if (has_signal && get_signal(&ksig)) {
                /* Whee! Actually deliver the signal.  */
                handle_signal(&ksig, regs);
                return;

diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 474f296..b9711e8 100644 (file)
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -37,6 +37,10 @@
 # define _TIF_UPROBE                   (0)
 #endif
 
+#ifndef _TIF_NOTIFY_SIGNAL
+# define _TIF_NOTIFY_SIGNAL            (0)
+#endif
+
 /*
  * TIF flags handled in syscall_enter_from_user_mode()
  */
@@ -69,7 +73,7 @@
 
 #define EXIT_TO_USER_MODE_WORK                                         \
        (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE |           \
-        _TIF_NEED_RESCHED | _TIF_PATCH_PENDING |                       \
+        _TIF_NEED_RESCHED | _TIF_PATCH_PENDING | _TIF_NOTIFY_SIGNAL |  \
         ARCH_EXIT_TO_USER_MODE_WORK)
 
 /**
@@ -259,12 +263,13 @@ static __always_inline void arch_exit_to_user_mode(void) { }
 #endif
 
 /**
- * arch_do_signal -  Architecture specific signal delivery function
+ * arch_do_signal_or_restart -  Architecture specific signal delivery function
  * @regs:      Pointer to currents pt_regs
+ * @has_signal:        actual signal to handle
  *
  * Invoked from exit_to_user_mode_loop().
  */
-void arch_do_signal(struct pt_regs *regs);
+void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal);
 
 /**
  * arch_syscall_exit_tracehook - Wrapper around tracehook_report_syscall_exit()

diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h
index 0cef17a..9b93f85 100644 (file)
--- a/include/linux/entry-kvm.h
+++ b/include/linux/entry-kvm.h
@@ -11,8 +11,8 @@
 # define ARCH_XFER_TO_GUEST_MODE_WORK  (0)
 #endif
 
-#define XFER_TO_GUEST_MODE_WORK                                        \
-       (_TIF_NEED_RESCHED | _TIF_SIGPENDING |                  \
+#define XFER_TO_GUEST_MODE_WORK                                                \
+       (_TIF_NEED_RESCHED | _TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL |     \
         _TIF_NOTIFY_RESUME | ARCH_XFER_TO_GUEST_MODE_WORK)
 
 struct kvm_vcpu;

diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index 1bad18a..bd5afa0 100644 (file)
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -353,11 +353,25 @@ static inline int restart_syscall(void)
        return -ERESTARTNOINTR;
 }
 
-static inline int signal_pending(struct task_struct *p)
+static inline int task_sigpending(struct task_struct *p)
 {
        return unlikely(test_tsk_thread_flag(p,TIF_SIGPENDING));
 }
 
+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
+        * so that notify signal callbacks can be processed.
+        */
+       if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL)))
+               return 1;
+#endif
+       return task_sigpending(p);
+}
+
 static inline int __fatal_signal_pending(struct task_struct *p)
 {
        return unlikely(sigismember(&p->pending.signal, SIGKILL));
@@ -365,7 +379,7 @@ static inline int __fatal_signal_pending(struct task_struct *p)
 
 static inline int fatal_signal_pending(struct task_struct *p)
 {
-       return signal_pending(p) && __fatal_signal_pending(p);
+       return task_sigpending(p) && __fatal_signal_pending(p);
 }
 
 static inline int signal_pending_state(long state, struct task_struct *p)
@@ -502,7 +516,7 @@ extern int set_user_sigmask(const sigset_t __user *umask, size_t sigsetsize);
 static inline void restore_saved_sigmask_unless(bool interrupted)
 {
        if (interrupted)
-               WARN_ON(!test_thread_flag(TIF_SIGPENDING));
+               WARN_ON(!signal_pending(current));
        else
                restore_saved_sigmask();
 }

diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index b480e1a..f7d82e4 100644 (file)
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -198,4 +198,31 @@ static inline void tracehook_notify_resume(struct pt_regs *regs)
        blkcg_maybe_throttle_current();
 }
 
+/*
+ * 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)
+{
+#if defined(TIF_NOTIFY_SIGNAL)
+       clear_thread_flag(TIF_NOTIFY_SIGNAL);
+       smp_mb__after_atomic();
+       if (current->task_works)
+               task_work_run();
+#endif
+}
+
+/*
+ * Called when we have work to process from exit_to_user_mode_loop()
+ */
+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 /* <linux/tracehook.h> */

diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index e9e2df3..3a1dfec 100644 (file)
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -135,7 +135,15 @@ static __always_inline void exit_to_user_mode(void)
 }
 
 /* Workaround to allow gradual conversion of architecture code */
-void __weak arch_do_signal(struct pt_regs *regs) { }
+void __weak arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { }
+
+static void handle_signal_work(struct pt_regs *regs, unsigned long ti_work)
+{
+       if (ti_work & _TIF_NOTIFY_SIGNAL)
+               tracehook_notify_signal();
+
+       arch_do_signal_or_restart(regs, ti_work & _TIF_SIGPENDING);
+}
 
 static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
                                            unsigned long ti_work)
@@ -157,8 +165,8 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
                if (ti_work & _TIF_PATCH_PENDING)
                        klp_update_patch_state(current);
 
-               if (ti_work & _TIF_SIGPENDING)
-                       arch_do_signal(regs);
+               if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
+                       handle_signal_work(regs, ti_work);
 
                if (ti_work & _TIF_NOTIFY_RESUME) {
                        tracehook_notify_resume(regs);
@@ -319,7 +327,7 @@ noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
                /*
                 * If RCU is not watching then the same careful
                 * sequence vs. lockdep and tracing is required
-                * as in irq_enter_from_user_mode().
+                * as in irqentry_enter_from_user_mode().
                 */
                lockdep_hardirqs_off(CALLER_ADDR0);
                rcu_irq_enter();

diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c
index b6678a5..49972ee 100644 (file)
--- a/kernel/entry/kvm.c
+++ b/kernel/entry/kvm.c
@@ -8,6 +8,9 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
        do {
                int ret;
 
+               if (ti_work & _TIF_NOTIFY_SIGNAL)
+                       tracehook_notify_signal();
+
                if (ti_work & _TIF_SIGPENDING) {
                        kvm_handle_signal_exit(vcpu);
                        return -EINTR;

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 00b0358..bf9edd8 100644 (file)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1973,7 +1973,7 @@ bool uprobe_deny_signal(void)
 
        WARN_ON_ONCE(utask->state != UTASK_SSTEP);
 
-       if (signal_pending(t)) {
+       if (task_sigpending(t)) {
                spin_lock_irq(&t->sighand->siglock);
                clear_tsk_thread_flag(t, TIF_SIGPENDING);
                spin_unlock_irq(&t->sighand->siglock);

diff --git a/kernel/signal.c b/kernel/signal.c
index a38b3ed..f67ea9a 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -983,7 +983,7 @@ static inline bool wants_signal(int sig, struct task_struct *p)
        if (task_is_stopped_or_traced(p))
                return false;
 
-       return task_curr(p) || !signal_pending(p);
+       return task_curr(p) || !task_sigpending(p);
 }
 
 static void complete_signal(int sig, struct task_struct *p, enum pid_type type)
@@ -2529,6 +2529,20 @@ bool get_signal(struct ksignal *ksig)
        struct signal_struct *signal = current->signal;
        int signr;
 
+       /*
+        * For non-generic architectures, check for TIF_NOTIFY_SIGNAL so
+        * 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;
 
@@ -2822,7 +2836,7 @@ static void retarget_shared_pending(struct task_struct *tsk, sigset_t *which)
                /* Remove the signals this thread can handle. */
                sigandsets(&retarget, &retarget, &t->blocked);
 
-               if (!signal_pending(t))
+               if (!task_sigpending(t))
                        signal_wake_up(t, 0);
 
                if (sigisemptyset(&retarget))
@@ -2856,7 +2870,7 @@ void exit_signals(struct task_struct *tsk)
 
        cgroup_threadgroup_change_end(tsk);
 
-       if (!signal_pending(tsk))
+       if (!task_sigpending(tsk))
                goto out;
 
        unblocked = tsk->blocked;
@@ -2900,7 +2914,7 @@ long do_no_restart_syscall(struct restart_block *param)
 
 static void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset)
 {
-       if (signal_pending(tsk) && !thread_group_empty(tsk)) {
+       if (task_sigpending(tsk) && !thread_group_empty(tsk)) {
                sigset_t newblocked;
                /* A set of now blocked but previously unblocked signals. */
                sigandnsets(&newblocked, newset, &current->blocked);

diff --git a/kernel/task_work.c b/kernel/task_work.c
index 8d6e121..15b0872 100644 (file)
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -5,6 +5,34 @@
 
 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
@@ -33,7 +61,6 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
                  enum task_work_notify_mode notify)
 {
        struct callback_head *head;
-       unsigned long flags;
 
        do {
                head = READ_ONCE(task->task_works);
@@ -49,17 +76,7 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
                set_notify_resume(task);
                break;
        case TWA_SIGNAL:
-               /*
-                * 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);
-               }
+               task_work_notify_signal(task);
                break;
        default:
                WARN_ON_ONCE(1);