[patch V2 02/29] perf/x86/intel: Sanitize PMU HT bug workaround

Thomas Gleixner
2017-09-12T19:49:11Z

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From: Peter Zijlstra <peterz@infradead.org>

The lockup_detector_suspend/resume() interface is broken in several ways
especially as it results in recursive locking of the CPU hotplug lock.

Use the new stop/restart interface in the perf NMI watchdog to temporarily
disable and reenable the already active watchdog events. That's enough to
handle it.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20170831073053.111536870@linutronix.de

---
arch/x86/events/intel/core.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)

--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -4409,10 +4409,9 @@ static __init int fixup_ht_bug(void)
return 0;
}

- if (lockup_detector_suspend() != 0) {
- pr_debug("failed to disable PMU erratum BJ122, BV98, HSD29 workaround\n");
- return 0;
- }
+ cpus_read_lock();
+
+ hardlockup_detector_perf_stop();

x86_pmu.flags &= ~(PMU_FL_EXCL_CNTRS | PMU_FL_EXCL_ENABLED);

@@ -4420,9 +4419,7 @@ static __init int fixup_ht_bug(void)
x86_pmu.commit_scheduling = NULL;
x86_pmu.stop_scheduling = NULL;

- lockup_detector_resume();
-
- cpus_read_lock();
+ hardlockup_detector_perf_restart();

for_each_online_cpu(c)
free_excl_cntrs(c);