From: Sudeep Holla <sudeep.holla@arm.com>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: joelaf@google.com, Cheng Jian <cj.chengjian@huawei.com>,
peterz@infradead.org, fweisbec@gmail.com,
huawei.libin@huawei.com, joel@joelfernandes.org,
mingo@kernel.org, aubrey.li@linux.intel.com,
naravamudan@digitalocean.com, aaron.lwe@gmail.com,
torvalds@linux-foundation.org, jdesfossez@digitalocean.com,
w.f@huawei.com, pawan.kumar.gupta@linux.intel.com,
pjt@google.com, kerrnel@google.com, keescook@chromium.org,
xiexiuqi@huawei.com, vpillai@digitalocean.com,
tglx@linutronix.de, linux-arm-kernel@lists.infradead.org,
pauld@redhat.com, mgorman@techsingularity.net,
linux-kernel@vger.kernel.org, aubrey.intel@gmail.com,
Sudeep Holla <sudeep.holla@arm.com>,
pbonzini@redhat.com, tim.c.chen@linux.intel.com
Subject: Re: [PATCH] sched/arm64: store cpu topology before notify_cpu_starting
Date: Thu, 9 Apr 2020 10:59:41 +0100 [thread overview]
Message-ID: <20200409095941.GA25948@bogus> (raw)
In-Reply-To: <jhjwo6zjq5m.mognet@arm.com>
On Wed, Apr 01, 2020 at 02:23:33PM +0100, Valentin Schneider wrote:
>
> (+LAKML, +Sudeep)
>
Thanks Valentin.
> On Wed, Apr 01 2020, Cheng Jian wrote:
> > when SCHED_CORE enabled, sched_cpu_starting() uses thread_sibling as
> > SMT_MASK to initialize rq->core, but only after store_cpu_topology(),
> > the thread_sibling is ready for use.
> >
> > notify_cpu_starting()
> > -> sched_cpu_starting() # use thread_sibling
> >
> > store_cpu_topology(cpu)
> > -> update_siblings_masks # set thread_sibling
> >
> > Fix this by doing notify_cpu_starting later, just like x86 do.
> >
>
> I haven't been following the sched core stuff closely; can't this
> rq->core assignment be done in sched_cpu_activate() instead? We already
> look at the cpu_smt_mask() in there, and it is valid (we go through the
> entirety of secondary_start_kernel() before getting anywhere near
> CPUHP_AP_ACTIVE).
>
I too came to same conclusion. Did you see any issues ? Or is it
just code inspection in parity with x86 ?
> I don't think this breaks anything, but without this dependency in
> sched_cpu_starting() then there isn't really a reason for this move.
>
Based on the commit message, had a quick look at x86 code and I agree
this shouldn't break anything. However the commit message does make
complete sense to me, especially reference to sched_cpu_starting
while smt_masks are accessed in sched_cpu_activate. Or am I missing
to understand something here ?
--
Regards,
Sudeep
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next prev parent reply other threads:[~2020-04-09 9:59 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <855831b59e1b3774b11c3e33050eac4cc4639f06.1583332765.git.vpillai@digitalocean.com>
[not found] ` <20200401114215.36640-1-cj.chengjian@huawei.com>
2020-04-01 13:23 ` [PATCH] sched/arm64: store cpu topology before notify_cpu_starting Valentin Schneider
2020-04-06 8:00 ` chengjian (D)
2020-04-09 9:59 ` Sudeep Holla [this message]
2020-04-09 10:32 ` Valentin Schneider
2020-04-09 11:08 ` Sudeep Holla
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