Commit 2406e3b1 authored Sep 12, 2017 by Peter Zijlstra Committed by Ingo Molnar Sep 14, 2017

perf/x86/intel, watchdog/core: Sanitize PMU HT bug workaround



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>
Reviewed-by: Don Zickus <dzickus@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Link: http://lkml.kernel.org/r/20170912194146.247141871@linutronix.de


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent d0b6e0a8

arch/x86/events/intel/core.c

+4 −7

Original line number	Diff line number	Diff line
		@@ -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);