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Merge branch 'urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

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Pull RCU fixes from Paul McKenney:

 - fix regressions induced by a merge-window change in scheduler
   semantics, which means that smp_processor_id() can no longer be used
   in kthreads using simple affinity to bind themselves to a specific
   CPU.

 - fix a bug in Tasks Trace RCU that was thought to be strictly
   theoretical. However, production workloads have started hitting this,
   so these fixes need to be merged sooner rather than later.

 - fix a minor printk()-format-mismatch issue introduced during the
   merge window.

* 'urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  rcu: Fix pr_info() formats and values in show_rcu_gp_kthreads()
  rcu-tasks: Don't delete holdouts within trc_wait_for_one_reader()
  rcu-tasks: Don't delete holdouts within trc_inspect_reader()
  refscale: Avoid false-positive warnings in ref_scale_reader()
  scftorture: Avoid false-positive warnings in scftorture_invoker()
This commit is contained in:
Linus Torvalds 2021-07-16 11:08:57 -07:00
commit 6e442d0662
4 changed files with 10 additions and 12 deletions
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6
kernel/rcu/refscale.c
View File

@ -487,13 +487,13 @@ ref_scale_reader(void *arg)
s64 duration;
VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: task started", me);
set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
WARN_ON_ONCE(set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids)));
set_user_nice(current, MAX_NICE);
atomic_inc(&n_init);
if (holdoff)
schedule_timeout_interruptible(holdoff * HZ);
repeat:
VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: waiting to start next experiment on cpu %d", me, smp_processor_id());
VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: waiting to start next experiment on cpu %d", me, raw_smp_processor_id());
// Wait for signal that this reader can start.
wait_event(rt->wq, (atomic_read(&nreaders_exp) && smp_load_acquire(&rt->start_reader)) ||
@ -503,7 +503,7 @@ repeat:
goto end;
// Make sure that the CPU is affinitized appropriately during testing.
WARN_ON_ONCE(smp_processor_id() != me);
WARN_ON_ONCE(raw_smp_processor_id() != me);
WRITE_ONCE(rt->start_reader, 0);
if (!atomic_dec_return(&n_started))

6
kernel/rcu/tasks.h
View File

@ -953,10 +953,9 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg)
in_qs = likely(!t->trc_reader_nesting);
}
// Mark as checked. Because this is called from the grace-period
// kthread, also remove the task from the holdout list.
// Mark as checked so that the grace-period kthread will
// remove it from the holdout list.
t->trc_reader_checked = true;
trc_del_holdout(t);
if (in_qs)
return true; // Already in quiescent state, done!!!
@ -983,7 +982,6 @@ static void trc_wait_for_one_reader(struct task_struct *t,
// The current task had better be in a quiescent state.
if (t == current) {
t->trc_reader_checked = true;
trc_del_holdout(t);
WARN_ON_ONCE(t->trc_reader_nesting);
return;
}

4
kernel/rcu/tree_stall.h
View File

@ -795,9 +795,9 @@ void show_rcu_gp_kthreads(void)
jr = j - data_race(rcu_state.gp_req_activity);
js = j - data_race(rcu_state.gp_start);
jw = j - data_race(rcu_state.gp_wake_time);
pr_info("%s: wait state: %s(%d) ->state: %#lx ->rt_priority %u delta ->gp_start %lu ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_max %lu ->gp_flags %#x\n",
pr_info("%s: wait state: %s(%d) ->state: %#x ->rt_priority %u delta ->gp_start %lu ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_max %lu ->gp_flags %#x\n",
rcu_state.name, gp_state_getname(rcu_state.gp_state),
rcu_state.gp_state, t ? t->__state : 0x1ffffL, t ? t->rt_priority : 0xffU,
rcu_state.gp_state, t ? t->__state : 0x1ffff, t ? t->rt_priority : 0xffU,
js, ja, jr, jw, (long)data_race(rcu_state.gp_wake_seq),
(long)data_race(rcu_state.gp_seq),
(long)data_race(rcu_get_root()->gp_seq_needed),

6
kernel/scftorture.c
View File

@ -405,15 +405,15 @@ static int scftorture_invoker(void *arg)
VERBOSE_SCFTORTOUT("scftorture_invoker %d: task started", scfp->cpu);
cpu = scfp->cpu % nr_cpu_ids;
set_cpus_allowed_ptr(current, cpumask_of(cpu));
WARN_ON_ONCE(set_cpus_allowed_ptr(current, cpumask_of(cpu)));
set_user_nice(current, MAX_NICE);
if (holdoff)
schedule_timeout_interruptible(holdoff * HZ);
VERBOSE_SCFTORTOUT("scftorture_invoker %d: Waiting for all SCF torturers from cpu %d", scfp->cpu, smp_processor_id());
VERBOSE_SCFTORTOUT("scftorture_invoker %d: Waiting for all SCF torturers from cpu %d", scfp->cpu, raw_smp_processor_id());
// Make sure that the CPU is affinitized appropriately during testing.
curcpu = smp_processor_id();
curcpu = raw_smp_processor_id();
WARN_ONCE(curcpu != scfp->cpu % nr_cpu_ids,
"%s: Wanted CPU %d, running on %d, nr_cpu_ids = %d\n",
__func__, scfp->cpu, curcpu, nr_cpu_ids);