* [PATCH resend] sched/smt: fix unbalance sched_smt_present dec/inc
@ 2024-07-02 8:11 Yang Yingliang
2024-07-02 8:44 ` Peter Zijlstra
0 siblings, 1 reply; 3+ messages in thread
From: Yang Yingliang @ 2024-07-02 8:11 UTC (permalink / raw)
To: linux-kernel
Cc: mingo, peterz, juri.lelli, vincent.guittot, dietmar.eggemann,
rostedt, bsegall, mgorman, bristot, vschneid, tglx, yu.c.chen,
tim.c.chen, yangyingliang, liwei391
From: Yang Yingliang <yangyingliang@huawei.com>
I got the following warn report while doing stress test:
jump label: negative count!
WARNING: CPU: 3 PID: 38 at kernel/jump_label.c:263 static_key_slow_try_dec+0x9d/0xb0
Call Trace:
<TASK>
__static_key_slow_dec_cpuslocked+0x16/0x70
sched_cpu_deactivate+0x26e/0x2a0
cpuhp_invoke_callback+0x3ad/0x10d0
cpuhp_thread_fun+0x3f5/0x680
smpboot_thread_fn+0x56d/0x8d0
kthread+0x309/0x400
ret_from_fork+0x41/0x70
ret_from_fork_asm+0x1b/0x30
</TASK>
Because when cpuset_cpu_inactive() fails in sched_cpu_deactivate(),
the cpu offline failed, but sched_smt_present is decremented before
calling sched_cpu_deactivate(), it leads to unbalanced dec/inc, so
fix it by incrementing sched_smt_present in the error path.
Fixes: c5511d03ec09 ("sched/smt: Make sched_smt_present track topology")
Reviewed-by: Chen Yu <yu.c.chen@intel.com>
Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
kernel/sched/core.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index bcf2c4cc0522..5ab6717b57e0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9756,6 +9756,10 @@ int sched_cpu_deactivate(unsigned int cpu)
sched_update_numa(cpu, false);
ret = cpuset_cpu_inactive(cpu);
if (ret) {
+#ifdef CONFIG_SCHED_SMT
+ if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
+ static_branch_inc_cpuslocked(&sched_smt_present);
+#endif
balance_push_set(cpu, false);
set_cpu_active(cpu, true);
sched_update_numa(cpu, true);
--
2.25.1
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH resend] sched/smt: fix unbalance sched_smt_present dec/inc 2024-07-02 8:11 [PATCH resend] sched/smt: fix unbalance sched_smt_present dec/inc Yang Yingliang @ 2024-07-02 8:44 ` Peter Zijlstra 2024-07-02 11:38 ` yangyingliang 0 siblings, 1 reply; 3+ messages in thread From: Peter Zijlstra @ 2024-07-02 8:44 UTC (permalink / raw) To: Yang Yingliang Cc: linux-kernel, mingo, juri.lelli, vincent.guittot, dietmar.eggemann, rostedt, bsegall, mgorman, bristot, vschneid, tglx, yu.c.chen, tim.c.chen, yangyingliang, liwei391 On Tue, Jul 02, 2024 at 04:11:28PM +0800, Yang Yingliang wrote: > From: Yang Yingliang <yangyingliang@huawei.com> > > I got the following warn report while doing stress test: > > jump label: negative count! > WARNING: CPU: 3 PID: 38 at kernel/jump_label.c:263 static_key_slow_try_dec+0x9d/0xb0 > Call Trace: > <TASK> > __static_key_slow_dec_cpuslocked+0x16/0x70 > sched_cpu_deactivate+0x26e/0x2a0 > cpuhp_invoke_callback+0x3ad/0x10d0 > cpuhp_thread_fun+0x3f5/0x680 > smpboot_thread_fn+0x56d/0x8d0 > kthread+0x309/0x400 > ret_from_fork+0x41/0x70 > ret_from_fork_asm+0x1b/0x30 > </TASK> > > Because when cpuset_cpu_inactive() fails in sched_cpu_deactivate(), > the cpu offline failed, but sched_smt_present is decremented before > calling sched_cpu_deactivate(), it leads to unbalanced dec/inc, so > fix it by incrementing sched_smt_present in the error path. > > Fixes: c5511d03ec09 ("sched/smt: Make sched_smt_present track topology") > Reviewed-by: Chen Yu <yu.c.chen@intel.com> > Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com> > Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> > --- > kernel/sched/core.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index bcf2c4cc0522..5ab6717b57e0 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -9756,6 +9756,10 @@ int sched_cpu_deactivate(unsigned int cpu) > sched_update_numa(cpu, false); > ret = cpuset_cpu_inactive(cpu); > if (ret) { > +#ifdef CONFIG_SCHED_SMT > + if (cpumask_weight(cpu_smt_mask(cpu)) == 2) > + static_branch_inc_cpuslocked(&sched_smt_present); > +#endif > balance_push_set(cpu, false); > set_cpu_active(cpu, true); > sched_update_numa(cpu, true); Yes, does indeed appear needed, however!, when I look at what else goes before this failure, should we not also call set_rq_online() and things like that? That is, can we rework things to be less fragile by sharing code between this error path and sched_cpu_activate() ? ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH resend] sched/smt: fix unbalance sched_smt_present dec/inc 2024-07-02 8:44 ` Peter Zijlstra @ 2024-07-02 11:38 ` yangyingliang 0 siblings, 0 replies; 3+ messages in thread From: yangyingliang @ 2024-07-02 11:38 UTC (permalink / raw) To: Peter Zijlstra Cc: linux-kernel, mingo, juri.lelli, vincent.guittot, dietmar.eggemann, rostedt, bsegall, mgorman, bristot, vschneid, tglx, yu.c.chen, tim.c.chen, yangyingliang, liwei391 > -----Original Messages----- > From: "Peter Zijlstra" <peterz@infradead.org> > Sent Time: 2024-07-02 16:44:18 (Tuesday) > To: "Yang Yingliang" <yangyingliang@huaweicloud.com> > Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, tglx@linutronix.de, yu.c.chen@intel.com, tim.c.chen@linux.intel.com, yangyingliang@huawei.com, liwei391@huawei.com > Subject: Re: [PATCH resend] sched/smt: fix unbalance sched_smt_present dec/inc > > On Tue, Jul 02, 2024 at 04:11:28PM +0800, Yang Yingliang wrote: > > From: Yang Yingliang <yangyingliang@huawei.com> > > > > I got the following warn report while doing stress test: > > > > jump label: negative count! > > WARNING: CPU: 3 PID: 38 at kernel/jump_label.c:263 static_key_slow_try_dec+0x9d/0xb0 > > Call Trace: > > <task> > > __static_key_slow_dec_cpuslocked+0x16/0x70 > > sched_cpu_deactivate+0x26e/0x2a0 > > cpuhp_invoke_callback+0x3ad/0x10d0 > > cpuhp_thread_fun+0x3f5/0x680 > > smpboot_thread_fn+0x56d/0x8d0 > > kthread+0x309/0x400 > > ret_from_fork+0x41/0x70 > > ret_from_fork_asm+0x1b/0x30 > > </task> > > > > Because when cpuset_cpu_inactive() fails in sched_cpu_deactivate(), > > the cpu offline failed, but sched_smt_present is decremented before > > calling sched_cpu_deactivate(), it leads to unbalanced dec/inc, so > > fix it by incrementing sched_smt_present in the error path. > > > > Fixes: c5511d03ec09 ("sched/smt: Make sched_smt_present track topology") > > Reviewed-by: Chen Yu <yu.c.chen@intel.com> > > Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com> > > Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> > > --- > > kernel/sched/core.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > index bcf2c4cc0522..5ab6717b57e0 100644 > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -9756,6 +9756,10 @@ int sched_cpu_deactivate(unsigned int cpu) > > sched_update_numa(cpu, false); > > ret = cpuset_cpu_inactive(cpu); > > if (ret) { > > +#ifdef CONFIG_SCHED_SMT > > + if (cpumask_weight(cpu_smt_mask(cpu)) == 2) > > + static_branch_inc_cpuslocked(&sched_smt_present); > > +#endif > > balance_push_set(cpu, false); > > set_cpu_active(cpu, true); > > sched_update_numa(cpu, true); > > Yes, does indeed appear needed, however!, when I look at > what else goes before this failure, should we not also call > set_rq_online() and things like that? Yes, set_rq_online() is needed in the error path. I will send a new patch to add this. > > That is, can we rework things to be less fragile by sharing code between > this error path and sched_cpu_activate() ? </yangyingliang@huawei.com></tim.c.chen@linux.intel.com></yu.c.chen@intel.com></yangyingliang@huawei.com></yangyingliang@huaweicloud.com></peterz@infradead.org> ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2024-07-02 11:38 UTC | newest] Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2024-07-02 8:11 [PATCH resend] sched/smt: fix unbalance sched_smt_present dec/inc Yang Yingliang 2024-07-02 8:44 ` Peter Zijlstra 2024-07-02 11:38 ` yangyingliang
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