Eric Lee / linux-smarc-t335x-v3.2

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Commit b58f6b0dd3d677338b9065388cc2cc942b86338e

Authored by Peter Zijlstra
Committed by Ingo Molnar
1 parent 3ce2a0bc9d
Exists in master and in 4 other branches v3.2_AM335xPSP_04.06.00.11, v3.2_NEWT335xPSP_04.06.00.11, v3.2_SBC_SMARTMEN, v3.2_SMARCT335xPSP_04.06.00.11

perf, core: Fix initial task_ctx/event installation 

A lost Quilt refresh of 2c29ef0fef8 (perf: Simplify and fix
__perf_install_in_context()) is causing grief and lockups,
reported by Jiri Olsa.

When installing an event in a task context, there's a number of
issues:

 - there might not be an existing task context, in which case
   we should install the now current context;

 - there might already be a context, not the current one, in
   which case we should de-schedule the old and install the new;

these cases were dealt with in the lost refresh, however there is one
further case that was found in testing:

 - there might already be a context, the current one, in which
   case we should still de-schedule, and should take care
   to re-install it (note that task_ctx_sched_out() clears
   cpuctx->task_ctx).

Reported-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1307399008.2497.971.camel@laptop
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Showing 1 changed file with 17 additions and 11 deletions Side-by-side Diff

kernel/events/core.c
Diff comments   View file @ b58f6b0
... ... @@ -1505,25 +1505,31 @@
1505 1505 struct perf_event_context *task_ctx = cpuctx->task_ctx;
1506 1506 struct task_struct *task = current;
1507 1507  
1508   - perf_ctx_lock(cpuctx, cpuctx->task_ctx);
  1508 + perf_ctx_lock(cpuctx, task_ctx);
1509 1509 perf_pmu_disable(cpuctx->ctx.pmu);
1510 1510  
1511 1511 /*
1512 1512 * If there was an active task_ctx schedule it out.
1513 1513 */
1514   - if (task_ctx) {
  1514 + if (task_ctx)
1515 1515 task_ctx_sched_out(task_ctx);
1516   - /*
1517   - * If the context we're installing events in is not the
1518   - * active task_ctx, flip them.
1519   - */
1520   - if (ctx->task && task_ctx != ctx) {
1521   - raw_spin_unlock(&cpuctx->ctx.lock);
1522   - raw_spin_lock(&ctx->lock);
1523   - cpuctx->task_ctx = task_ctx = ctx;
1524   - }
  1516 +
  1517 + /*
  1518 + * If the context we're installing events in is not the
  1519 + * active task_ctx, flip them.
  1520 + */
  1521 + if (ctx->task && task_ctx != ctx) {
  1522 + if (task_ctx)
  1523 + raw_spin_unlock(&task_ctx->lock);
  1524 + raw_spin_lock(&ctx->lock);
  1525 + task_ctx = ctx;
  1526 + }
  1527 +
  1528 + if (task_ctx) {
  1529 + cpuctx->task_ctx = task_ctx;
1525 1530 task = task_ctx->task;
1526 1531 }
  1532 +
1527 1533 cpu_ctx_sched_out(cpuctx, EVENT_ALL);
1528 1534  
1529 1535 update_context_time(ctx);