linux-kernel - [tip:perfcounters/core] perf_counter: fix print debug irq disable

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Date:	Wed, 13 May 2009 06:21:47 GMT
From:	tip-bot for Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de, mingo@...e.hu
Subject: [tip:perfcounters/core] perf_counter: fix print debug irq disable

Commit-ID:  5bb9efe33ea4001a17ab98186a40a134a3061d67
Gitweb:     http://git.kernel.org/tip/5bb9efe33ea4001a17ab98186a40a134a3061d67
Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Wed, 13 May 2009 08:12:51 +0200
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 13 May 2009 08:17:37 +0200

perf_counter: fix print debug irq disable

inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
bash/15802 [HC0[0]:SC0[0]:HE1:SE1] takes:
 (sysrq_key_table_lock){?.....},

Don't unconditionally enable interrupts in the perf_counter_print_debug()
path.

[ Impact: fix potential deadlock pointed out by lockdep ]

LKML-Reference: <new-submission>
Reported-by: Ingo Molnar <mingo@...e.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>


---
 arch/x86/kernel/cpu/perf_counter.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index da27419..f7772ff 100644
--- a/arch/x86/kernel/cpu/perf_counter.c
+++ b/arch/x86/kernel/cpu/perf_counter.c
@@ -621,12 +621,13 @@ void perf_counter_print_debug(void)
 {
 	u64 ctrl, status, overflow, pmc_ctrl, pmc_count, prev_left, fixed;
 	struct cpu_hw_counters *cpuc;
+	unsigned long flags;
 	int cpu, idx;
 
 	if (!x86_pmu.num_counters)
 		return;
 
-	local_irq_disable();
+	local_irq_save(flags);
 
 	cpu = smp_processor_id();
 	cpuc = &per_cpu(cpu_hw_counters, cpu);
@@ -664,7 +665,7 @@ void perf_counter_print_debug(void)
 		pr_info("CPU#%d: fixed-PMC%d count: %016llx\n",
 			cpu, idx, pmc_count);
 	}
-	local_irq_enable();
+	local_irq_restore(flags);
 }
 
 static void x86_pmu_disable(struct perf_counter *counter)
--
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