Dear RT folks!
I'm pleased to announce the v6.4-rc5-rt4 patch set.
Changes since v6.4-rc5-rt3:
- Drop the sigqueue caching patch which was introduced in
v6.3-rc5-rt8. After discussion with upstream it is probably not
worth it.
- Alternative fix for ptrace/ wait_task_inactive().
Known issues
None
The delta patch against v6.4-rc5-rt3 is appended below and can be found here:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/6.4/incr/patch-6.4-rc5-rt3-rt4.patch.xz
You can get this release via the git tree at:
git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git v6.4-rc5-rt4
The RT patch against v6.4-rc5 can be found here:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/6.4/older/patch-6.4-rc5-rt4.patch.xz
The split quilt queue is available at:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/6.4/older/patches-6.4-rc5-rt4.tar.xz
Sebastian
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f2e752377eadd..3ce3e07fbf6f5 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2011,15 +2011,12 @@ static __always_inline void scheduler_ipi(void)
*/
preempt_fold_need_resched();
}
-extern unsigned long wait_task_inactive(struct task_struct *, unsigned int match_state);
#else
static inline void scheduler_ipi(void) { }
-static inline unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state)
-{
- return 1;
-}
#endif
+extern unsigned long wait_task_inactive(struct task_struct *, unsigned int match_state);
+
/*
* Set thread flags in other task's structures.
* See asm/thread_info.h for TIF_xxxx flags available:
diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index b38ce53576000..669e8cff40c74 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -22,7 +22,6 @@ struct sighand_struct {
refcount_t count;
wait_queue_head_t signalfd_wqh;
struct k_sigaction action[_NSIG];
- struct sigqueue *sigqueue_cache;
};
/*
@@ -350,7 +349,6 @@ extern int send_sig(int, struct task_struct *, int);
extern int zap_other_threads(struct task_struct *p);
extern struct sigqueue *sigqueue_alloc(void);
extern void sigqueue_free(struct sigqueue *);
-extern void sigqueue_free_cached_entry(struct sigqueue *q);
extern int send_sigqueue(struct sigqueue *, struct pid *, enum pid_type);
extern int do_sigaction(int, struct k_sigaction *, struct k_sigaction *);
diff --git a/kernel/fork.c b/kernel/fork.c
index 4ba3b5c98ca09..81cba91f30bbe 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1814,7 +1814,6 @@ static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
RCU_INIT_POINTER(tsk->sighand, sig);
if (!sig)
return -ENOMEM;
- sig->sigqueue_cache = NULL;
refcount_set(&sig->count, 1);
spin_lock_irq(¤t->sighand->siglock);
@@ -1831,17 +1830,7 @@ static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
void __cleanup_sighand(struct sighand_struct *sighand)
{
if (refcount_dec_and_test(&sighand->count)) {
- struct sigqueue *sigqueue = NULL;
-
signalfd_cleanup(sighand);
- spin_lock_irq(&sighand->siglock);
- if (sighand->sigqueue_cache) {
- sigqueue = sighand->sigqueue_cache;
- sighand->sigqueue_cache = NULL;
- }
- spin_unlock_irq(&sighand->siglock);
-
- sigqueue_free_cached_entry(sigqueue);
/*
* sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
* without an RCU grace period, see __lock_task_sighand().
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 77cde41aeccab..c7c09f1db4572 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2253,6 +2253,154 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
rq_clock_skip_update(rq);
}
+static __always_inline
+int __task_state_match(struct task_struct *p, unsigned int state)
+{
+ if (READ_ONCE(p->__state) & state)
+ return 1;
+
+#ifdef CONFIG_PREEMPT_RT
+ if (READ_ONCE(p->saved_state) & state)
+ return -1;
+#endif
+ return 0;
+}
+
+static __always_inline
+int task_state_match(struct task_struct *p, unsigned int state)
+{
+#ifdef CONFIG_PREEMPT_RT
+ int match;
+
+ /*
+ * Serialize against current_save_and_set_rtlock_wait_state() and
+ * current_restore_rtlock_saved_state().
+ */
+ raw_spin_lock_irq(&p->pi_lock);
+ match = __task_state_match(p, state);
+ raw_spin_unlock_irq(&p->pi_lock);
+
+ return match;
+#else
+ return __task_state_match(p, state);
+#endif
+}
+
+/*
+ * wait_task_inactive - wait for a thread to unschedule.
+ *
+ * Wait for the thread to block in any of the states set in @match_state.
+ * If it changes, i.e. @p might have woken up, then return zero. When we
+ * succeed in waiting for @p to be off its CPU, we return a positive number
+ * (its total switch count). If a second call a short while later returns the
+ * same number, the caller can be sure that @p has remained unscheduled the
+ * whole time.
+ *
+ * The caller must ensure that the task *will* unschedule sometime soon,
+ * else this function might spin for a *long* time. This function can't
+ * be called with interrupts off, or it may introduce deadlock with
+ * smp_call_function() if an IPI is sent by the same process we are
+ * waiting to become inactive.
+ */
+unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state)
+{
+ int running, queued, match;
+ struct rq_flags rf;
+ unsigned long ncsw;
+ struct rq *rq;
+
+ for (;;) {
+ /*
+ * We do the initial early heuristics without holding
+ * any task-queue locks at all. We'll only try to get
+ * the runqueue lock when things look like they will
+ * work out!
+ */
+ rq = task_rq(p);
+
+ /*
+ * If the task is actively running on another CPU
+ * still, just relax and busy-wait without holding
+ * any locks.
+ *
+ * NOTE! Since we don't hold any locks, it's not
+ * even sure that "rq" stays as the right runqueue!
+ * But we don't care, since "task_on_cpu()" will
+ * return false if the runqueue has changed and p
+ * is actually now running somewhere else!
+ */
+ while (task_on_cpu(rq, p)) {
+ if (!task_state_match(p, match_state))
+ return 0;
+ cpu_relax();
+ }
+
+ /*
+ * Ok, time to look more closely! We need the rq
+ * lock now, to be *sure*. If we're wrong, we'll
+ * just go back and repeat.
+ */
+ rq = task_rq_lock(p, &rf);
+ trace_sched_wait_task(p);
+ running = task_on_cpu(rq, p);
+ queued = task_on_rq_queued(p);
+ ncsw = 0;
+ if ((match = __task_state_match(p, match_state))) {
+ /*
+ * When matching on p->saved_state, consider this task
+ * still queued so it will wait.
+ */
+ if (match < 0)
+ queued = 1;
+ ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
+ }
+ task_rq_unlock(rq, p, &rf);
+
+ /*
+ * If it changed from the expected state, bail out now.
+ */
+ if (unlikely(!ncsw))
+ break;
+
+ /*
+ * Was it really running after all now that we
+ * checked with the proper locks actually held?
+ *
+ * Oops. Go back and try again..
+ */
+ if (unlikely(running)) {
+ cpu_relax();
+ continue;
+ }
+
+ /*
+ * It's not enough that it's not actively running,
+ * it must be off the runqueue _entirely_, and not
+ * preempted!
+ *
+ * So if it was still runnable (but just not actively
+ * running right now), it's preempted, and we should
+ * yield - it could be a while.
+ */
+ if (unlikely(queued)) {
+ ktime_t to = NSEC_PER_SEC / HZ;
+
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ schedule_hrtimeout(&to, HRTIMER_MODE_REL_HARD);
+ continue;
+ }
+
+ /*
+ * Ahh, all good. It wasn't running, and it wasn't
+ * runnable, which means that it will never become
+ * running in the future either. We're all done!
+ */
+ break;
+ }
+
+ return ncsw;
+}
+
#ifdef CONFIG_SMP
static void
@@ -3383,185 +3531,6 @@ int migrate_swap(struct task_struct *cur, struct task_struct *p,
}
#endif /* CONFIG_NUMA_BALANCING */
-#ifdef CONFIG_PREEMPT_RT
-
-/*
- * Consider:
- *
- * set_special_state(X);
- *
- * do_things()
- * // Somewhere in there is an rtlock that can be contended:
- * current_save_and_set_rtlock_wait_state();
- * [...]
- * schedule_rtlock(); (A)
- * [...]
- * current_restore_rtlock_saved_state();
- *
- * schedule(); (B)
- *
- * If p->saved_state is anything else than TASK_RUNNING, then p blocked on an
- * rtlock (A) *before* voluntarily calling into schedule() (B) after setting its
- * state to X. For things like ptrace (X=TASK_TRACED), the task could have more
- * work to do upon acquiring the lock in do_things() before whoever called
- * wait_task_inactive() should return. IOW, we have to wait for:
- *
- * p.saved_state = TASK_RUNNING
- * p.__state = X
- *
- * which implies the task isn't blocked on an RT lock and got to schedule() (B).
- *
- * Also see comments in ttwu_state_match().
- */
-
-static __always_inline bool state_mismatch(struct task_struct *p, unsigned int match_state)
-{
- unsigned long flags;
- bool mismatch;
-
- raw_spin_lock_irqsave(&p->pi_lock, flags);
- if (READ_ONCE(p->__state) & match_state)
- mismatch = false;
- else if (READ_ONCE(p->saved_state) & match_state)
- mismatch = false;
- else
- mismatch = true;
-
- raw_spin_unlock_irqrestore(&p->pi_lock, flags);
- return mismatch;
-}
-static __always_inline bool state_match(struct task_struct *p, unsigned int match_state,
- bool *wait)
-{
- if (READ_ONCE(p->__state) & match_state)
- return true;
- if (READ_ONCE(p->saved_state) & match_state) {
- *wait = true;
- return true;
- }
- return false;
-}
-#else
-static __always_inline bool state_mismatch(struct task_struct *p, unsigned int match_state)
-{
- return !(READ_ONCE(p->__state) & match_state);
-}
-static __always_inline bool state_match(struct task_struct *p, unsigned int match_state,
- bool *wait)
-{
- return (READ_ONCE(p->__state) & match_state);
-}
-#endif
-
-/*
- * wait_task_inactive - wait for a thread to unschedule.
- *
- * Wait for the thread to block in any of the states set in @match_state.
- * If it changes, i.e. @p might have woken up, then return zero. When we
- * succeed in waiting for @p to be off its CPU, we return a positive number
- * (its total switch count). If a second call a short while later returns the
- * same number, the caller can be sure that @p has remained unscheduled the
- * whole time.
- *
- * The caller must ensure that the task *will* unschedule sometime soon,
- * else this function might spin for a *long* time. This function can't
- * be called with interrupts off, or it may introduce deadlock with
- * smp_call_function() if an IPI is sent by the same process we are
- * waiting to become inactive.
- */
-unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state)
-{
- bool running, wait;
- struct rq_flags rf;
- unsigned long ncsw;
- struct rq *rq;
-
- for (;;) {
- /*
- * We do the initial early heuristics without holding
- * any task-queue locks at all. We'll only try to get
- * the runqueue lock when things look like they will
- * work out!
- */
- rq = task_rq(p);
-
- /*
- * If the task is actively running on another CPU
- * still, just relax and busy-wait without holding
- * any locks.
- *
- * NOTE! Since we don't hold any locks, it's not
- * even sure that "rq" stays as the right runqueue!
- * But we don't care, since "task_on_cpu()" will
- * return false if the runqueue has changed and p
- * is actually now running somewhere else!
- */
- while (task_on_cpu(rq, p)) {
- if (state_mismatch(p, match_state))
- return 0;
- cpu_relax();
- }
-
- /*
- * Ok, time to look more closely! We need the rq
- * lock now, to be *sure*. If we're wrong, we'll
- * just go back and repeat.
- */
- rq = task_rq_lock(p, &rf);
- trace_sched_wait_task(p);
- running = task_on_cpu(rq, p);
- wait = task_on_rq_queued(p);
- ncsw = 0;
-
- if (state_match(p, match_state, &wait))
- ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
- task_rq_unlock(rq, p, &rf);
-
- /*
- * If it changed from the expected state, bail out now.
- */
- if (unlikely(!ncsw))
- break;
-
- /*
- * Was it really running after all now that we
- * checked with the proper locks actually held?
- *
- * Oops. Go back and try again..
- */
- if (unlikely(running)) {
- cpu_relax();
- continue;
- }
-
- /*
- * It's not enough that it's not actively running,
- * it must be off the runqueue _entirely_, and not
- * preempted!
- *
- * So if it was still runnable (but just not actively
- * running right now), it's preempted, and we should
- * yield - it could be a while.
- */
- if (unlikely(wait)) {
- ktime_t to = NSEC_PER_SEC / HZ;
-
- set_current_state(TASK_UNINTERRUPTIBLE);
- schedule_hrtimeout(&to, HRTIMER_MODE_REL_HARD);
- continue;
- }
-
- /*
- * Ahh, all good. It wasn't running, and it wasn't
- * runnable, which means that it will never become
- * running in the future either. We're all done!
- */
- break;
- }
-
- return ncsw;
-}
-
/***
* kick_process - kick a running thread to enter/exit the kernel
* @p: the to-be-kicked thread
@@ -4116,15 +4085,14 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
static __always_inline
bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success)
{
+ int match;
+
if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)) {
WARN_ON_ONCE((state & TASK_RTLOCK_WAIT) &&
state != TASK_RTLOCK_WAIT);
}
- if (READ_ONCE(p->__state) & state) {
- *success = 1;
- return true;
- }
+ *success = !!(match = __task_state_match(p, state));
#ifdef CONFIG_PREEMPT_RT
/*
@@ -4140,12 +4108,10 @@ bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success)
* p::saved_state to TASK_RUNNING so any further tests will
* not result in false positives vs. @success
*/
- if (p->saved_state & state) {
+ if (match < 0)
p->saved_state = TASK_RUNNING;
- *success = 1;
- }
#endif
- return false;
+ return match > 0;
}
/*
diff --git a/kernel/signal.c b/kernel/signal.c
index 5ba6cb05ff4f5..9e07b3075c72e 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -432,18 +432,7 @@ __sigqueue_alloc(int sig, struct task_struct *t, gfp_t gfp_flags,
return NULL;
if (override_rlimit || likely(sigpending <= task_rlimit(t, RLIMIT_SIGPENDING))) {
-
- if (!sigqueue_flags) {
- struct sighand_struct *sighand = t->sighand;
-
- lockdep_assert_held(&sighand->siglock);
- if (sighand->sigqueue_cache) {
- q = sighand->sigqueue_cache;
- sighand->sigqueue_cache = NULL;
- }
- }
- if (!q)
- q = kmem_cache_alloc(sigqueue_cachep, gfp_flags);
+ q = kmem_cache_alloc(sigqueue_cachep, gfp_flags);
} else {
print_dropped_signal(sig);
}
@@ -458,43 +447,14 @@ __sigqueue_alloc(int sig, struct task_struct *t, gfp_t gfp_flags,
return q;
}
-static bool sigqueue_cleanup_accounting(struct sigqueue *q)
+static void __sigqueue_free(struct sigqueue *q)
{
if (q->flags & SIGQUEUE_PREALLOC)
- return false;
+ return;
if (q->ucounts) {
dec_rlimit_put_ucounts(q->ucounts, UCOUNT_RLIMIT_SIGPENDING);
q->ucounts = NULL;
}
- return true;
-}
-
-static void __sigqueue_free(struct sigqueue *q)
-{
- if (!sigqueue_cleanup_accounting(q))
- return;
- kmem_cache_free(sigqueue_cachep, q);
-}
-
-void sigqueue_free_cached_entry(struct sigqueue *q)
-{
- if (!q)
- return;
- kmem_cache_free(sigqueue_cachep, q);
-}
-
-static void sigqueue_cache_or_free(struct sigqueue *q)
-{
- struct sighand_struct *sighand = current->sighand;
-
- if (!sigqueue_cleanup_accounting(q))
- return;
-
- lockdep_assert_held(&sighand->siglock);
- if (!sighand->sigqueue_cache) {
- sighand->sigqueue_cache = q;
- return;
- }
kmem_cache_free(sigqueue_cachep, q);
}
@@ -634,7 +594,7 @@ static void collect_signal(int sig, struct sigpending *list, kernel_siginfo_t *i
(info->si_code == SI_TIMER) &&
(info->si_sys_private);
- sigqueue_cache_or_free(first);
+ __sigqueue_free(first);
} else {
/*
* Ok, it wasn't in the queue. This must be
diff --git a/localversion-rt b/localversion-rt
index 1445cd65885cd..ad3da1bcab7e8 100644
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt3
+-rt4
