Dear RT folks!
I'm pleased to announce the v4.19.23-rt14 patch set.
Changes since v4.19.23-rt13:
- Use the specified preempt mask in should_resched() on x86. Otherwise
a scheduling opportunity of non RT tasks could be missed.
- Preserve the task state in cpu_chill()
- Add two more cases to consider before warning about pending
softirqs.
Known issues
- A warning triggered in "rcu_note_context_switch" originated from
SyS_timer_gettime(). The issue was always there, it is now
visible. Reported by Grygorii Strashko and Daniel Wagner.
The delta patch against v4.19.23-rt13 is appended below and can be found here:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.19/incr/patch-4.19.23-rt13-rt14.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
v4.19.23-rt14
The RT patch against v4.19.23 can be found here:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patch-4.19.23-rt14.patch.xz
The split quilt queue is available at:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.23-rt14.tar.xz
Sebastian
diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index 22992c8377952..f667087792747 100644
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -118,7 +118,7 @@ static __always_inline bool should_resched(int
preempt_offset)
/* preempt count == 0 ? */
tmp &= ~PREEMPT_NEED_RESCHED;
- if (tmp)
+ if (tmp != preempt_offset)
return false;
if (current_thread_info()->preempt_lazy_count)
return false;
diff --git a/kernel/softirq.c b/kernel/softirq.c
index c15583162a559..25bcf2f2714ba 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -92,6 +92,34 @@ static inline void softirq_clr_runner(unsigned int sirq)
sr->runner[sirq] = NULL;
}
+static bool softirq_check_runner_tsk(struct task_struct *tsk,
+ unsigned int *pending)
+{
+ bool ret = false;
+
+ if (!tsk)
+ return ret;
+
+ /*
+ * The wakeup code in rtmutex.c wakes up the task
+ * _before_ it sets pi_blocked_on to NULL under
+ * tsk->pi_lock. So we need to check for both: state
+ * and pi_blocked_on.
+ * The test against UNINTERRUPTIBLE + ->sleeping_lock is in case the
+ * task does cpu_chill().
+ */
+ raw_spin_lock(&tsk->pi_lock);
+ if (tsk->pi_blocked_on || tsk->state == TASK_RUNNING ||
+ (tsk->state == TASK_UNINTERRUPTIBLE && tsk->sleeping_lock)) {
+ /* Clear all bits pending in that task */
+ *pending &= ~(tsk->softirqs_raised);
+ ret = true;
+ }
+ raw_spin_unlock(&tsk->pi_lock);
+
+ return ret;
+}
+
/*
* On preempt-rt a softirq running context might be blocked on a
* lock. There might be no other runnable task on this CPU because the
@@ -104,6 +132,7 @@ static inline void softirq_clr_runner(unsigned int sirq)
*/
void softirq_check_pending_idle(void)
{
+ struct task_struct *tsk;
static int rate_limit;
struct softirq_runner *sr = this_cpu_ptr(&softirq_runners);
u32 warnpending;
@@ -113,24 +142,23 @@ void softirq_check_pending_idle(void)
return;
warnpending = local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK;
+ if (!warnpending)
+ return;
for (i = 0; i < NR_SOFTIRQS; i++) {
- struct task_struct *tsk = sr->runner[i];
+ tsk = sr->runner[i];
- /*
- * The wakeup code in rtmutex.c wakes up the task
- * _before_ it sets pi_blocked_on to NULL under
- * tsk->pi_lock. So we need to check for both: state
- * and pi_blocked_on.
- */
- if (tsk) {
- raw_spin_lock(&tsk->pi_lock);
- if (tsk->pi_blocked_on || tsk->state == TASK_RUNNING) {
- /* Clear all bits pending in that task */
- warnpending &= ~(tsk->softirqs_raised);
- warnpending &= ~(1 << i);
- }
- raw_spin_unlock(&tsk->pi_lock);
- }
+ if (softirq_check_runner_tsk(tsk, &warnpending))
+ warnpending &= ~(1 << i);
+ }
+
+ if (warnpending) {
+ tsk = __this_cpu_read(ksoftirqd);
+ softirq_check_runner_tsk(tsk, &warnpending);
+ }
+
+ if (warnpending) {
+ tsk = __this_cpu_read(ktimer_softirqd);
+ softirq_check_runner_tsk(tsk, &warnpending);
}
if (warnpending) {
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 851b2134e77f4..6f2736ec4b8ef 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1902,15 +1902,18 @@ void cpu_chill(void)
{
ktime_t chill_time;
unsigned int freeze_flag = current->flags & PF_NOFREEZE;
+ long saved_state;
+ saved_state = current->state;
chill_time = ktime_set(0, NSEC_PER_MSEC);
- set_current_state(TASK_UNINTERRUPTIBLE);
+ __set_current_state_no_track(TASK_UNINTERRUPTIBLE);
current->flags |= PF_NOFREEZE;
sleeping_lock_inc();
schedule_hrtimeout(&chill_time, HRTIMER_MODE_REL_HARD);
sleeping_lock_dec();
if (!freeze_flag)
current->flags &= ~PF_NOFREEZE;
+ __set_current_state_no_track(saved_state);
}
EXPORT_SYMBOL(cpu_chill);
#endif
diff --git a/localversion-rt b/localversion-rt
index 9f7d0bdbffb18..08b3e75841adc 100644
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt13
+-rt14
