hw-breakpoints: Fix task-bound breakpoint slot allocation
Whatever the context nature of a breakpoint, we always perform the
following constraint checks before allocating it a slot:
- Check the number of pinned breakpoint bound the concerned cpus
- Check the max number of task-bound breakpoints that are belonging
to a task.
- Add both and see if we have a reamining slot for the new breakpoint
This is the right thing to do when we are about to register a cpu-only
bound breakpoint. But not if we are dealing with a task bound
breakpoint. What we want in this case is:
- Check the number of pinned breakpoint bound the concerned cpus
- Check the number of breakpoints that already belong to the task
in which the breakpoint to register is bound to.
- Add both
This fixes a regression that makes the "firefox -g" command fail to
register breakpoints once we deal with a secondary thread.
Reported-by: Walt <w41ter@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c
index b600fc2..02b4925 100644
--- a/kernel/hw_breakpoint.c
+++ b/kernel/hw_breakpoint.c
@@ -83,50 +83,16 @@
return 0;
}
-/*
- * Report the number of pinned/un-pinned breakpoints we have in
- * a given cpu (cpu > -1) or in all of them (cpu = -1).
- */
-static void fetch_bp_busy_slots(struct bp_busy_slots *slots, int cpu)
+static int task_bp_pinned(struct task_struct *tsk)
{
- if (cpu >= 0) {
- slots->pinned = per_cpu(nr_cpu_bp_pinned, cpu);
- slots->pinned += max_task_bp_pinned(cpu);
- slots->flexible = per_cpu(nr_bp_flexible, cpu);
-
- return;
- }
-
- for_each_online_cpu(cpu) {
- unsigned int nr;
-
- nr = per_cpu(nr_cpu_bp_pinned, cpu);
- nr += max_task_bp_pinned(cpu);
-
- if (nr > slots->pinned)
- slots->pinned = nr;
-
- nr = per_cpu(nr_bp_flexible, cpu);
-
- if (nr > slots->flexible)
- slots->flexible = nr;
- }
-}
-
-/*
- * Add a pinned breakpoint for the given task in our constraint table
- */
-static void toggle_bp_task_slot(struct task_struct *tsk, int cpu, bool enable)
-{
- int count = 0;
- struct perf_event *bp;
struct perf_event_context *ctx = tsk->perf_event_ctxp;
- unsigned int *tsk_pinned;
struct list_head *list;
+ struct perf_event *bp;
unsigned long flags;
+ int count = 0;
if (WARN_ONCE(!ctx, "No perf context for this task"))
- return;
+ return 0;
list = &ctx->event_list;
@@ -143,8 +109,58 @@
spin_unlock_irqrestore(&ctx->lock, flags);
- if (WARN_ONCE(count < 0, "No breakpoint counter found in the counter list"))
+ return count;
+}
+
+/*
+ * Report the number of pinned/un-pinned breakpoints we have in
+ * a given cpu (cpu > -1) or in all of them (cpu = -1).
+ */
+static void
+fetch_bp_busy_slots(struct bp_busy_slots *slots, struct perf_event *bp)
+{
+ int cpu = bp->cpu;
+ struct task_struct *tsk = bp->ctx->task;
+
+ if (cpu >= 0) {
+ slots->pinned = per_cpu(nr_cpu_bp_pinned, cpu);
+ if (!tsk)
+ slots->pinned += max_task_bp_pinned(cpu);
+ else
+ slots->pinned += task_bp_pinned(tsk);
+ slots->flexible = per_cpu(nr_bp_flexible, cpu);
+
return;
+ }
+
+ for_each_online_cpu(cpu) {
+ unsigned int nr;
+
+ nr = per_cpu(nr_cpu_bp_pinned, cpu);
+ if (!tsk)
+ nr += max_task_bp_pinned(cpu);
+ else
+ nr += task_bp_pinned(tsk);
+
+ if (nr > slots->pinned)
+ slots->pinned = nr;
+
+ nr = per_cpu(nr_bp_flexible, cpu);
+
+ if (nr > slots->flexible)
+ slots->flexible = nr;
+ }
+}
+
+/*
+ * Add a pinned breakpoint for the given task in our constraint table
+ */
+static void toggle_bp_task_slot(struct task_struct *tsk, int cpu, bool enable)
+{
+ unsigned int *tsk_pinned;
+ int count = 0;
+
+ count = task_bp_pinned(tsk);
tsk_pinned = per_cpu(task_bp_pinned, cpu);
if (enable) {
@@ -233,7 +249,7 @@
mutex_lock(&nr_bp_mutex);
- fetch_bp_busy_slots(&slots, bp->cpu);
+ fetch_bp_busy_slots(&slots, bp);
/* Flexible counters need to keep at least one slot */
if (slots.pinned + (!!slots.flexible) == HBP_NUM) {
