perf/x86: Add sanity checks to x86_schedule_events()

By computing the 'committed' index earlier, we can use it to validate
the cached constraint state.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index fa88acf0daadf0897c340fd39015e8a18f622be9..24dab9ad4fd66a97cfcb009feb4b19fa411214c5 100644 (file)
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -849,17 +849,34 @@ int x86_schedule_events(struct cpu_hw_events *cpuc, int n, int *assign)
        struct event_constraint *c;
        unsigned long used_mask[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
        struct perf_event *e;
-       int i, wmin, wmax, unsched = 0;
+       int n0, i, wmin, wmax, unsched = 0;
        struct hw_perf_event *hwc;
 
        bitmap_zero(used_mask, X86_PMC_IDX_MAX);
 
+       /*
+        * Compute the number of events already present; see x86_pmu_add(),
+        * validate_group() and x86_pmu_commit_txn(). For the former two
+        * cpuc->n_events hasn't been updated yet, while for the latter
+        * cpuc->n_txn contains the number of events added in the current
+        * transaction.
+        */
+       n0 = cpuc->n_events;
+       if (cpuc->txn_flags & PERF_PMU_TXN_ADD)
+               n0 -= cpuc->n_txn;
+
        if (x86_pmu.start_scheduling)
                x86_pmu.start_scheduling(cpuc);
 
        for (i = 0, wmin = X86_PMC_IDX_MAX, wmax = 0; i < n; i++) {
                c = cpuc->event_constraint[i];
 
+               /*
+                * Previously scheduled events should have a cached constraint,
+                * while new events should not have one.
+                */
+               WARN_ON_ONCE((c && i >= n0) || (!c && i < n0));
+
                /*
                 * Request constraints for new events; or for those events that
                 * have a dynamic constraint -- for those the constraint can
@@ -937,18 +954,7 @@ int x86_schedule_events(struct cpu_hw_events *cpuc, int n, int *assign)
                                x86_pmu.commit_scheduling(cpuc, i, assign[i]);
                }
        } else {
-               /*
-                * Compute the number of events already present; see
-                * x86_pmu_add(), validate_group() and x86_pmu_commit_txn().
-                * For the former two cpuc->n_events hasn't been updated yet,
-                * while for the latter cpuc->n_txn contains the number of
-                * events added in the current transaction.
-                */
-               i = cpuc->n_events;
-               if (cpuc->txn_flags & PERF_PMU_TXN_ADD)
-                       i -= cpuc->n_txn;
-
-               for (; i < n; i++) {
+               for (i = n0; i < n; i++) {
                        e = cpuc->event_list[i];
 
                        /*