[tip:perfcounters/core] perf_counter: x86: Protect against infinite loops in intel_pmu_handle_irq()

tip-bot for Ingo Molnar
2009-05-15T08:47:49Z

Commit-ID: 9029a5e3801f1cc7cdaab80169d82427acf928d8
Gitweb: http://git.kernel.org/tip/9029a5e3801f1cc7cdaab80169d82427acf928d8
Author: Ingo Molnar <mingo@elte.hu>
AuthorDate: Fri, 15 May 2009 08:26:20 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 15 May 2009 09:47:06 +0200

perf_counter: x86: Protect against infinite loops in intel_pmu_handle_irq()

intel_pmu_handle_irq() can lock up in an infinite loop if the hardware
does not allow the acking of irqs. Alas, this happened in testing so
make this robust and emit a warning if it happens in the future.

Also, clean up the IRQ handlers a bit.

[ Impact: improve perfcounter irq/nmi handling robustness ]

Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
arch/x86/kernel/cpu/perf_counter.c | 25 ++++++++++++++++++-------
1 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index 46a82d1..5a7f718 100644
--- a/arch/x86/kernel/cpu/perf_counter.c
+++ b/arch/x86/kernel/cpu/perf_counter.c
@@ -722,9 +722,13 @@ static void intel_pmu_save_and_restart(struct perf_counter *counter)
*/
static int intel_pmu_handle_irq(struct pt_regs *regs, int nmi)
{
- int bit, cpu = smp_processor_id();
+ struct cpu_hw_counters *cpuc;
+ struct cpu_hw_counters;
+ int bit, cpu, loops;
u64 ack, status;
- struct cpu_hw_counters *cpuc = &per_cpu(cpu_hw_counters, cpu);
+
+ cpu = smp_processor_id();
+ cpuc = &per_cpu(cpu_hw_counters, cpu);

perf_disable();
status = intel_pmu_get_status();
@@ -733,7 +737,13 @@ static int intel_pmu_handle_irq(struct pt_regs *regs, int nmi)
return 0;
}

+ loops = 0;
again:
+ if (++loops > 100) {
+ WARN_ONCE(1, "perfcounters: irq loop stuck!\n");
+ return 1;
+ }
+
inc_irq_stat(apic_perf_irqs);
ack = status;
for_each_bit(bit, (unsigned long *)&status, X86_PMC_IDX_MAX) {
@@ -765,13 +775,14 @@ again:

static int amd_pmu_handle_irq(struct pt_regs *regs, int nmi)
{
- int cpu = smp_processor_id();
- struct cpu_hw_counters *cpuc = &per_cpu(cpu_hw_counters, cpu);
- u64 val;
- int handled = 0;
+ int cpu, idx, throttle = 0, handled = 0;
+ struct cpu_hw_counters *cpuc;
struct perf_counter *counter;
struct hw_perf_counter *hwc;
- int idx, throttle = 0;
+ u64 val;
+
+ cpu = smp_processor_id();
+ cpuc = &per_cpu(cpu_hw_counters, cpu);

if (++cpuc->interrupts == PERFMON_MAX_INTERRUPTS) {
throttle = 1;