linux-kernel - [tip:smp/hotplug] perf/x86/intel: Drop get_online_cpus() in intel_snb_check

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Date:   Fri, 26 May 2017 01:41:42 -0700
From:   tip-bot for Sebastian Andrzej Siewior <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     mingo@...nel.org, paulmck@...ux.vnet.ibm.com,
        linux-kernel@...r.kernel.org, tglx@...utronix.de,
        rostedt@...dmis.org, hpa@...or.com, bp@...e.de,
        bigeasy@...utronix.de, bp@...en8.de, peterz@...radead.org
Subject: [tip:smp/hotplug] perf/x86/intel: Drop get_online_cpus() in
 intel_snb_check_microcode()

Commit-ID:  1ba143a5216fb148211160a0ecc1f8d3f92f06bb
Gitweb:     http://git.kernel.org/tip/1ba143a5216fb148211160a0ecc1f8d3f92f06bb
Author:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
AuthorDate: Wed, 24 May 2017 10:15:30 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 26 May 2017 10:10:43 +0200

perf/x86/intel: Drop get_online_cpus() in intel_snb_check_microcode()

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@...utronix.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Ingo Molnar <mingo@...nel.org>
Acked-by: Borislav Petkov <bp@...e.de>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Borislav Petkov <bp@...en8.de>
Link: http://lkml.kernel.org/r/20170524081548.594862191@linutronix.de

---
 arch/x86/events/intel/core.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index a6d91d4..b9174aa 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3410,12 +3410,10 @@ static void intel_snb_check_microcode(void)
 	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, u64 mask)
 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;
 }