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Message-ID: <CAP-5=fWBVm08LetcyRUh6MK+_gQmyJYxR2sfeZ8LvXfeeJs=zg@mail.gmail.com>
Date: Wed, 20 Jul 2022 08:22:56 -0700
From: Ian Rogers <irogers@...gle.com>
To: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Marco Elver <elver@...gle.com>,
Peter Zijlstra <peterz@...radead.org>,
Frederic Weisbecker <frederic@...nel.org>,
Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
Michael Ellerman <mpe@...erman.id.au>,
linuxppc-dev@...ts.ozlabs.org, linux-perf-users@...r.kernel.org,
x86@...nel.org, linux-sh@...r.kernel.org,
kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 02/14] perf/hw_breakpoint: Provide hw_breakpoint_is_used()
and use in test
On Mon, Jul 4, 2022 at 8:10 AM Dmitry Vyukov <dvyukov@...gle.com> wrote:
>
> On Mon, 4 Jul 2022 at 17:06, Marco Elver <elver@...gle.com> wrote:
> >
> > Provide hw_breakpoint_is_used() to check if breakpoints are in use on
> > the system.
> >
> > Use it in the KUnit test to verify the global state before and after a
> > test case.
> >
> > Signed-off-by: Marco Elver <elver@...gle.com>
>
> Reviewed-by: Dmitry Vyukov <dvyukov@...gle.com>
Acked-by: Ian Rogers <irogers@...gle.com>
Thanks,
Ian
> > ---
> > v3:
> > * New patch.
> > ---
> > include/linux/hw_breakpoint.h | 3 +++
> > kernel/events/hw_breakpoint.c | 29 +++++++++++++++++++++++++++++
> > kernel/events/hw_breakpoint_test.c | 12 +++++++++++-
> > 3 files changed, 43 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h
> > index 78dd7035d1e5..a3fb846705eb 100644
> > --- a/include/linux/hw_breakpoint.h
> > +++ b/include/linux/hw_breakpoint.h
> > @@ -74,6 +74,7 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
> > extern int register_perf_hw_breakpoint(struct perf_event *bp);
> > extern void unregister_hw_breakpoint(struct perf_event *bp);
> > extern void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events);
> > +extern bool hw_breakpoint_is_used(void);
> >
> > extern int dbg_reserve_bp_slot(struct perf_event *bp);
> > extern int dbg_release_bp_slot(struct perf_event *bp);
> > @@ -121,6 +122,8 @@ register_perf_hw_breakpoint(struct perf_event *bp) { return -ENOSYS; }
> > static inline void unregister_hw_breakpoint(struct perf_event *bp) { }
> > static inline void
> > unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events) { }
> > +static inline bool hw_breakpoint_is_used(void) { return false; }
> > +
> > static inline int
> > reserve_bp_slot(struct perf_event *bp) {return -ENOSYS; }
> > static inline void release_bp_slot(struct perf_event *bp) { }
> > diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
> > index f32320ac02fd..fd5cd1f9e7fc 100644
> > --- a/kernel/events/hw_breakpoint.c
> > +++ b/kernel/events/hw_breakpoint.c
> > @@ -604,6 +604,35 @@ void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)
> > }
> > EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);
> >
> > +/**
> > + * hw_breakpoint_is_used - check if breakpoints are currently used
> > + *
> > + * Returns: true if breakpoints are used, false otherwise.
> > + */
> > +bool hw_breakpoint_is_used(void)
> > +{
> > + int cpu;
> > +
> > + if (!constraints_initialized)
> > + return false;
> > +
> > + for_each_possible_cpu(cpu) {
> > + for (int type = 0; type < TYPE_MAX; ++type) {
> > + struct bp_cpuinfo *info = get_bp_info(cpu, type);
> > +
> > + if (info->cpu_pinned)
> > + return true;
> > +
> > + for (int slot = 0; slot < nr_slots[type]; ++slot) {
> > + if (info->tsk_pinned[slot])
> > + return true;
> > + }
> > + }
> > + }
> > +
> > + return false;
> > +}
> > +
> > static struct notifier_block hw_breakpoint_exceptions_nb = {
> > .notifier_call = hw_breakpoint_exceptions_notify,
> > /* we need to be notified first */
> > diff --git a/kernel/events/hw_breakpoint_test.c b/kernel/events/hw_breakpoint_test.c
> > index 433c5c45e2a5..5ced822df788 100644
> > --- a/kernel/events/hw_breakpoint_test.c
> > +++ b/kernel/events/hw_breakpoint_test.c
> > @@ -294,7 +294,14 @@ static struct kunit_case hw_breakpoint_test_cases[] = {
> > static int test_init(struct kunit *test)
> > {
> > /* Most test cases want 2 distinct CPUs. */
> > - return num_online_cpus() < 2 ? -EINVAL : 0;
> > + if (num_online_cpus() < 2)
> > + return -EINVAL;
> > +
> > + /* Want the system to not use breakpoints elsewhere. */
> > + if (hw_breakpoint_is_used())
> > + return -EBUSY;
> > +
> > + return 0;
> > }
> >
> > static void test_exit(struct kunit *test)
> > @@ -308,6 +315,9 @@ static void test_exit(struct kunit *test)
> > kthread_stop(__other_task);
> > __other_task = NULL;
> > }
> > +
> > + /* Verify that internal state agrees that no breakpoints are in use. */
> > + KUNIT_EXPECT_FALSE(test, hw_breakpoint_is_used());
> > }
> >
> > static struct kunit_suite hw_breakpoint_test_suite = {
> > --
> > 2.37.0.rc0.161.g10f37bed90-goog
> >
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