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Commit e1ebe862 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
Browse files

hw_breakpoint: Simplify list/idx mess in toggle_bp_slot() paths 



The enable/disable logic in toggle_bp_slot() is not symmetrical
and imho very confusing. "old_count" in toggle_bp_task_slot() is
actually new_count because this bp was already removed from the
list.

Change toggle_bp_slot() to always call list_add/list_del after
toggle_bp_task_slot(). This way old_idx is task_bp_pinned() and
this entry should be decremented, new_idx is +/-weight and we
need to increment this element. The code/logic looks obvious.

Reported-by: default avatarVince Weaver <vincent.weaver@maine.edu>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20130620155011.GA6330@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent f070a4db

kernel/events/hw_breakpoint.c

+16 −24
Original line number Diff line number Diff line
@@ -185,26 +185,20 @@ fetch_this_slot(struct bp_busy_slots *slots, int weight) 
static void toggle_bp_task_slot(struct perf_event *bp, int cpu, bool enable,

				enum bp_type_idx type, int weight)

{

	unsigned int *tsk_pinned;

	int old_count = 0;

	int old_idx = 0;

	int idx = 0;



	old_count = task_bp_pinned(cpu, bp, type);

	old_idx = old_count - 1;

	idx = old_idx + weight;



	/* tsk_pinned[n] is the number of tasks having n breakpoints */

	tsk_pinned = per_cpu(nr_task_bp_pinned[type], cpu);

	if (enable) {

		tsk_pinned[idx]++;

		if (old_count > 0)

	/* tsk_pinned[n-1] is the number of tasks having n>0 breakpoints */

	unsigned int *tsk_pinned = per_cpu(nr_task_bp_pinned[type], cpu);

	int old_idx, new_idx;



	old_idx = task_bp_pinned(cpu, bp, type) - 1;

	if (enable)

		new_idx = old_idx + weight;

	else

		new_idx = old_idx - weight;



	if (old_idx >= 0)

		tsk_pinned[old_idx]--;

	} else {

		tsk_pinned[idx]--;

		if (old_count > 0)

			tsk_pinned[old_idx]++;

	}

	if (new_idx >= 0)

		tsk_pinned[new_idx]++;

}



/*
@@ -228,10 +222,6 @@ toggle_bp_slot(struct perf_event *bp, bool enable, enum bp_type_idx type, 
	}



	/* Pinned counter task profiling */



	if (!enable)

		list_del(&bp->hw.bp_list);



	if (cpu >= 0) {

		toggle_bp_task_slot(bp, cpu, enable, type, weight);

	} else {
@@ -241,6 +231,8 @@ toggle_bp_slot(struct perf_event *bp, bool enable, enum bp_type_idx type, 


	if (enable)

		list_add_tail(&bp->hw.bp_list, &bp_task_head);

	else

		list_del(&bp->hw.bp_list);

}



/*