| Date | Wed, 24 May 2017 10:15:30 +0200 | From | Thomas Gleixner <> | Subject | [patch V3 19/32] perf/x86/intel: Drop get_online_cpus() in intel_snb_check_microcode() |
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
If intel_snb_check_microcode() is invoked via microcode_init -> perf_check_microcode -> intel_snb_check_microcode
then get_online_cpus() is invoked nested. This works with the current implementation of get_online_cpus() but prevents converting it to a percpu rwsem.
intel_snb_check_microcode() is also invoked from intel_sandybridge_quirk() unprotected.
Drop get_online_cpus() from intel_snb_check_microcode() and add it to intel_sandybridge_quirk() so both call sites are protected.
Convert *_online_cpus() to the new interfaces while at it.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Borislav Petkov <bp@suse.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Borislav Petkov <bp@alien8.de>
--- arch/x86/events/intel/core.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-)
--- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -3410,12 +3410,10 @@ static void intel_snb_check_microcode(vo int pebs_broken = 0; int cpu; - get_online_cpus(); for_each_online_cpu(cpu) { if ((pebs_broken = intel_snb_pebs_broken(cpu))) break; } - put_online_cpus(); if (pebs_broken == x86_pmu.pebs_broken) return; @@ -3488,7 +3486,9 @@ static bool check_msr(unsigned long msr, static __init void intel_sandybridge_quirk(void) { x86_pmu.check_microcode = intel_snb_check_microcode; + cpus_read_lock(); intel_snb_check_microcode(); + cpus_read_unlock(); } static const struct { int id; char *name; } intel_arch_events_map[] __initconst = { @@ -4112,13 +4112,12 @@ static __init int fixup_ht_bug(void) lockup_detector_resume(); - get_online_cpus(); + cpus_read_lock(); - for_each_online_cpu(c) { + for_each_online_cpu(c) free_excl_cntrs(c); - } - put_online_cpus(); + cpus_read_unlock(); pr_info("PMU erratum BJ122, BV98, HSD29 workaround disabled, HT off\n"); return 0; }
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