perf_counter: powerpc: add nmi_enter/nmi_exit calls

Impact: fix potential deadlocks on powerpc

Now that the core is using in_nmi() (added in e30e08f6, "perf_counter:
fix NMI race in task clock"), we need the powerpc perf_counter_interrupt
to call nmi_enter() and nmi_exit() in those cases where the interrupt
happens when interrupts are soft-disabled.

If interrupts were soft-enabled, we can treat it as a regular interrupt
and do irq_enter/irq_exit around the whole routine. This lets us get rid
of the test_perf_counter_pending() call at the end of
perf_counter_interrupt, thus simplifying things a little.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <18909.31952.873098.336615@cargo.ozlabs.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 17 insertions, 14 deletions

diff --git a/arch/powerpc/kernel/perf_counter.c b/arch/powerpc/kernel/perf_counter.c
index c9d019f19074..bd76d0fa2c35 100644
--- a/arch/powerpc/kernel/perf_counter.c
+++ b/arch/powerpc/kernel/perf_counter.c
@@ -714,7 +714,7 @@ hw_perf_counter_init(struct perf_counter *counter)
  * here so there is no possibility of being interrupted.
  */
 static void record_and_restart(struct perf_counter *counter, long val,
-                               struct pt_regs *regs)
+                               struct pt_regs *regs, int nmi)
 {
         s64 prev, delta, left;
         int record = 0;
@@ -749,7 +749,7 @@ static void record_and_restart(struct perf_counter *counter, long val,
          * Finally record data if requested.
          */
         if (record)
-                perf_counter_overflow(counter, 1, regs, 0);
+                perf_counter_overflow(counter, nmi, regs, 0);
 }
 
 /*
@@ -762,6 +762,17 @@ static void perf_counter_interrupt(struct pt_regs *regs)
         struct perf_counter *counter;
         long val;
         int found = 0;
+        int nmi;
+
+        /*
+         * If interrupts were soft-disabled when this PMU interrupt
+         * occurred, treat it as an NMI.
+         */
+        nmi = !regs->softe;
+        if (nmi)
+                nmi_enter();
+        else
+                irq_enter();
 
         for (i = 0; i < cpuhw->n_counters; ++i) {
                 counter = cpuhw->counter[i];
@@ -769,7 +780,7 @@ static void perf_counter_interrupt(struct pt_regs *regs)
                 if ((int)val < 0) {
                         /* counter has overflowed */
                         found = 1;
-                        record_and_restart(counter, val, regs);
+                        record_and_restart(counter, val, regs, nmi);
                 }
         }
 
@@ -796,18 +807,10 @@ static void perf_counter_interrupt(struct pt_regs *regs)
          */
         mtspr(SPRN_MMCR0, cpuhw->mmcr[0]);
 
-        /*
-         * If we need a wakeup, check whether interrupts were soft-enabled
-         * when we took the interrupt.  If they were, we can wake stuff up
-         * immediately; otherwise we'll have do the wakeup when interrupts
-         * get soft-enabled.
-         */
-        if (test_perf_counter_pending() && regs->softe) {
-                irq_enter();
-                clear_perf_counter_pending();
-                perf_counter_do_pending();
+        if (nmi)
+                nmi_exit();
+        else
                 irq_exit();
-        }
 }
 
 void hw_perf_counter_setup(int cpu)