Messages in this thread | | | Date | Thu, 16 Sep 2021 11:57:44 +0800 | From | Pingfan Liu <> | Subject | Re: [PATCH 2/5] kernel/watchdog_hld: clarify the condition in hardlockup_detector_event_create() |
| |
On Wed, Sep 15, 2021 at 03:45:06PM +0200, Peter Zijlstra wrote: > On Wed, Sep 15, 2021 at 11:51:00AM +0800, Pingfan Liu wrote: > > hardlockup_detector_event_create() indirectly calls > > kmem_cache_alloc_node(), which is blockable. > > > > So here, the really planned context is is_percpu_thread(). > > > > Signed-off-by: Pingfan Liu <kernelfans@gmail.com> > > Cc: Petr Mladek <pmladek@suse.com> > > Cc: Andrew Morton <akpm@linux-foundation.org> > > Cc: Wang Qing <wangqing@vivo.com> > > Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org> > > Cc: Santosh Sivaraj <santosh@fossix.org> > > Cc: Sumit Garg <sumit.garg@linaro.org> > > Cc: Will Deacon <will@kernel.org> > > Cc: Mark Rutland <mark.rutland@arm.com> > > To: linux-kernel@vger.kernel.org > > --- > > kernel/watchdog_hld.c | 5 ++++- > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c > > index 247bf0b1582c..6876e796dbf5 100644 > > --- a/kernel/watchdog_hld.c > > +++ b/kernel/watchdog_hld.c > > @@ -165,10 +165,13 @@ static void watchdog_overflow_callback(struct perf_event *event, > > > > static int hardlockup_detector_event_create(void) > > { > > - unsigned int cpu = smp_processor_id(); > > + unsigned int cpu; > > struct perf_event_attr *wd_attr; > > struct perf_event *evt; > > > > + /* This function plans to execute in cpu bound kthread */ > > + BUG_ON(!is_percpu_thread()); > > + cpu = raw_smp_processor_id(); > > wd_attr = &wd_hw_attr; > > wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh); > > This patch makes no sense.
This patch aims to disable any attempt such as using get_cpu()/put_cpu() to shut up the check_preemption_disabled().
But if anybody is familiar with the integration of watchdog_hld and cpuhp, he should know the right way without this BUG_ON() or warn.
Do you still think it is pointless?
Thanks,
Pingfan
| |