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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>
This commit is contained in:
Frederic Weisbecker 2009-12-07 06:46:48 +01:00
parent ed872d09ef
commit 56053170ea
1 changed files with 56 additions and 40 deletions
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96
kernel/hw_breakpoint.c
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@ -83,50 +83,16 @@ static unsigned int max_task_bp_pinned(int cpu)
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 @@ static void toggle_bp_task_slot(struct task_struct *tsk, int cpu, bool enable)
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 @@ int reserve_bp_slot(struct perf_event *bp)
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) {