From 56053170ea2a2c0dc17420e9b94aa3ca51d80408 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Mon, 7 Dec 2009 06:46:48 +0100 Subject: [PATCH] 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 Signed-off-by: Frederic Weisbecker Cc: Prasad --- kernel/hw_breakpoint.c | 74 ++++++++++++++++++++++++++++++-------------------- 1 file changed, 45 insertions(+), 29 deletions(-) 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 @@ -83,15 +83,51 @@ static unsigned int max_task_bp_pinned(int cpu) return 0; } +static int task_bp_pinned(struct task_struct *tsk) +{ + struct perf_event_context *ctx = tsk->perf_event_ctxp; + 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 0; + + list = &ctx->event_list; + + spin_lock_irqsave(&ctx->lock, flags); + + /* + * The current breakpoint counter is not included in the list + * at the open() callback time + */ + list_for_each_entry(bp, list, event_entry) { + if (bp->attr.type == PERF_TYPE_BREAKPOINT) + count++; + } + + spin_unlock_irqrestore(&ctx->lock, flags); + + 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, int cpu) +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); - slots->pinned += max_task_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; @@ -101,7 +137,10 @@ static void fetch_bp_busy_slots(struct bp_busy_slots *slots, int cpu) unsigned int nr; nr = per_cpu(nr_cpu_bp_pinned, cpu); - nr += max_task_bp_pinned(cpu); + if (!tsk) + nr += max_task_bp_pinned(cpu); + else + nr += task_bp_pinned(tsk); if (nr > slots->pinned) slots->pinned = nr; @@ -118,33 +157,10 @@ static void fetch_bp_busy_slots(struct bp_busy_slots *slots, int cpu) */ 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; - unsigned long flags; - - if (WARN_ONCE(!ctx, "No perf context for this task")) - return; - - list = &ctx->event_list; - - spin_lock_irqsave(&ctx->lock, flags); - - /* - * The current breakpoint counter is not included in the list - * at the open() callback time - */ - list_for_each_entry(bp, list, event_entry) { - if (bp->attr.type == PERF_TYPE_BREAKPOINT) - count++; - } - - spin_unlock_irqrestore(&ctx->lock, flags); + int count = 0; - if (WARN_ONCE(count < 0, "No breakpoint counter found in the counter list")) - return; + 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) { -- 1.8.2.3