From: Peter Zijlstra <peterz@infradead.org>
To: Song Liu <songliubraving@fb.com>
Cc: bpf <bpf@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"acme@kernel.org" <acme@kernel.org>,
"mingo@redhat.com" <mingo@redhat.com>,
"kjain@linux.ibm.com" <kjain@linux.ibm.com>,
Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH v5 bpf-next 1/3] perf: enable branch record for software events
Date: Sat, 4 Sep 2021 12:18:34 +0200 [thread overview]
Message-ID: <20210904101834.GC4323@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <6BA620C1-D311-4992-8119-68A740ABA8BC@fb.com>
On Fri, Sep 03, 2021 at 04:45:29PM +0000, Song Liu wrote:
> Hi Peter,
>
> > On Sep 3, 2021, at 1:27 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > On Thu, Sep 02, 2021 at 09:57:04AM -0700, Song Liu wrote:
> >
> >> +static int
> >> +intel_pmu_snapshot_branch_stack(struct perf_branch_entry *entries, unsigned int cnt)
> >> +{
> >> + struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> >> +
> >> + intel_pmu_disable_all();
> >> + intel_pmu_lbr_read();
> >> + cnt = min_t(unsigned int, cnt, x86_pmu.lbr_nr);
> >> +
> >> + memcpy(entries, cpuc->lbr_entries, sizeof(struct perf_branch_entry) * cnt);
> >> + intel_pmu_enable_all(0);
> >> + return cnt;
> >> +}
> >
> > Given this disables the PMI from 'random' contexts, should we not add
> > IRQ disabling around this to avoid really bad behaviour?
>
> Do you mean we should add (instead of not add) IRQ disable?
Yeah, I tihnk we want local_irq_save()/restore() here.
next prev parent reply other threads:[~2021-09-04 10:19 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-02 16:57 [PATCH v5 bpf-next 0/3] bpf: introduce bpf_get_branch_snapshot Song Liu
2021-09-02 16:57 ` [PATCH v5 bpf-next 1/3] perf: enable branch record for software events Song Liu
2021-09-02 20:49 ` John Fastabend
2021-09-03 8:02 ` Peter Zijlstra
2021-09-03 16:50 ` Song Liu
2021-09-07 18:59 ` Song Liu
2021-09-07 20:50 ` Andrii Nakryiko
2021-09-03 8:27 ` Peter Zijlstra
2021-09-03 16:45 ` Song Liu
2021-09-04 10:18 ` Peter Zijlstra [this message]
2021-09-02 16:57 ` [PATCH v5 bpf-next 2/3] bpf: introduce helper bpf_get_branch_snapshot Song Liu
2021-09-02 20:56 ` John Fastabend
2021-09-02 22:04 ` Song Liu
2021-09-02 22:53 ` Andrii Nakryiko
2021-09-02 23:03 ` Song Liu
2021-09-02 23:05 ` Andrii Nakryiko
2021-09-03 1:03 ` Alexei Starovoitov
2021-09-03 8:28 ` Peter Zijlstra
2021-09-03 16:58 ` Song Liu
2021-09-03 8:47 ` Peter Zijlstra
2021-09-03 17:06 ` Song Liu
2021-09-03 17:10 ` Andrii Nakryiko
2021-09-04 10:24 ` Peter Zijlstra
2021-09-04 10:55 ` Peter Zijlstra
2021-09-02 16:57 ` [PATCH v5 bpf-next 3/3] selftests/bpf: add test for bpf_get_branch_snapshot Song Liu
2021-09-02 21:05 ` John Fastabend
2021-09-02 22:54 ` [PATCH v5 bpf-next 0/3] bpf: introduce bpf_get_branch_snapshot Andrii Nakryiko
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