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Message-ID: <20231024163450.GB13938@noisy.programming.kicks-ass.net>
Date: Tue, 24 Oct 2023 18:34:50 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Mario Limonciello <mario.limonciello@....com>
Cc: Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
Thomas Gleixner <tglx@...utronix.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Sandipan Das <sandipan.das@....com>,
"H . Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
x86@...nel.org, linux-pm@...r.kernel.org, rafael@...nel.org,
pavel@....cz, linux-perf-users@...r.kernel.org,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH 2/2] perf/x86/amd: Don't allow pre-emption in
amd_pmu_lbr_reset()
On Tue, Oct 24, 2023 at 06:30:38PM +0200, Peter Zijlstra wrote:
> On Tue, Oct 24, 2023 at 11:04:06AM -0500, Mario Limonciello wrote:
>
> > > IIRC this is the hotplug thread running a teardown function on that CPU
> > > itself. It being a strict per-cpu thread should not trip
> > > smp_processor_id() wanrs.
> > >
> >
> > BUG: using smp_processor_id() in preemptible [00000000] code: rtcwake/2960
> > caller is amd_pmu_lbr_reset+0x19/0xc0
> > CPU: 104 PID: 2960 Comm: rtcwake Not tainted 6.6.0-rc6-00002-g3e2c7f3ac51f
>
> Very much not the cpuhp/%u thread :/, let me try and figure out how that
> happens.
Uhh, my bad, these are the PREPARE/DEAD handlers, they run before online
and after dying. The CPU is completely dead. Running lbr_reset() here
makes no sense.
Did that want to be in amd_pmu_cpu_dying() ?
>
> > #1025
> > Call Trace:
> > <TASK>
> > dump_stack_lvl+0x44/0x60
> > check_preemption_disabled+0xce/0xf0
> > ? __pfx_x86_pmu_dead_cpu+0x10/0x10
> > amd_pmu_lbr_reset+0x19/0xc0
> > ? __pfx_x86_pmu_dead_cpu+0x10/0x10
> > amd_pmu_cpu_reset.constprop.0+0x51/0x60
> > amd_pmu_cpu_dead+0x3e/0x90
> > x86_pmu_dead_cpu+0x13/0x20
> > cpuhp_invoke_callback+0x169/0x4b0
> > ? __pfx_virtnet_cpu_dead+0x10/0x10
> > __cpuhp_invoke_callback_range+0x76/0xe0
> > _cpu_down+0x112/0x270
> > freeze_secondary_cpus+0x8e/0x280
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