From e1ebe86203e6532eb5a0ae8f26ccae47aca548ae Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Thu, 20 Jun 2013 17:50:11 +0200 Subject: [PATCH] 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: Vince Weaver Signed-off-by: Oleg Nesterov Acked-by: Frederic Weisbecker Link: http://lkml.kernel.org/r/20130620155011.GA6330@redhat.com Signed-off-by: Ingo Molnar --- kernel/events/hw_breakpoint.c | 40 ++++++++++++++--------------------- 1 file changed, 16 insertions(+), 24 deletions(-) diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c index ef8ebe560949..dee0148dcf54 100644 --- a/kernel/events/hw_breakpoint.c +++ b/kernel/events/hw_breakpoint.c @@ -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[old_idx]--; - } else { - tsk_pinned[idx]--; - if (old_count > 0) - tsk_pinned[old_idx]++; - } + /* 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]--; + 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); } /* -- 2.39.5