Commit-ID: 8bc2095951517e2c74b8aeeca4685ddd6b16ed4b
Gitweb: http://git.kernel.org/tip/8bc2095951517e2c74b8aeeca4685ddd6b16ed4b
Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
AuthorDate: Fri, 15 May 2009 20:45:59 +0200
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Sun, 17 May 2009 07:52:23 +0200
perf_counter: Fix inheritance cleanup code
Clean up code that open-coded the list_{add,del}_counter() code in
__perf_counter_exit_task() which consequently diverged. This could
lead to software counter crashes.
Also, fold the ctx->nr_counter inc/dec into those functions and clean
up some of the related code.
[ Impact: fix potential sw counter crash, cleanup ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Srivatsa Vaddagiri <vatsa@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Corey Ashford <cjashfor@xxxxxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/perf_counter.c | 32 +++++++++++++++-----------------
1 files changed, 15 insertions(+), 17 deletions(-)
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 57840a9..59a926d 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -115,6 +115,7 @@ list_add_counter(struct perf_counter *counter, struct perf_counter_context *ctx)
}
list_add_rcu(&counter->event_entry, &ctx->event_list);
+ ctx->nr_counters++;
}
static void
@@ -122,6 +123,8 @@ list_del_counter(struct perf_counter *counter, struct perf_counter_context *ctx)
{
struct perf_counter *sibling, *tmp;
+ ctx->nr_counters--;
+
list_del_init(&counter->list_entry);
list_del_rcu(&counter->event_entry);
@@ -209,7 +212,6 @@ static void __perf_counter_remove_from_context(void *info)
counter_sched_out(counter, cpuctx, ctx);
counter->task = NULL;
- ctx->nr_counters--;
/*
* Protect the list operation against NMI by disabling the
@@ -276,7 +278,6 @@ retry:
* succeed.
*/
if (!list_empty(&counter->list_entry)) {
- ctx->nr_counters--;
list_del_counter(counter, ctx);
counter->task = NULL;
}
@@ -544,7 +545,6 @@ static void add_counter_to_ctx(struct perf_counter *counter,
struct perf_counter_context *ctx)
{
list_add_counter(counter, ctx);
- ctx->nr_counters++;
counter->prev_state = PERF_COUNTER_STATE_OFF;
counter->tstamp_enabled = ctx->time;
counter->tstamp_running = ctx->time;
@@ -3206,9 +3206,8 @@ static int inherit_group(struct perf_counter *parent_counter,
static void sync_child_counter(struct perf_counter *child_counter,
struct perf_counter *parent_counter)
{
- u64 parent_val, child_val;
+ u64 child_val;
- parent_val = atomic64_read(&parent_counter->count);
child_val = atomic64_read(&child_counter->count);
/*
@@ -3240,7 +3239,6 @@ __perf_counter_exit_task(struct task_struct *child,
struct perf_counter_context *child_ctx)
{
struct perf_counter *parent_counter;
- struct perf_counter *sub, *tmp;
/*
* If we do not self-reap then we have to wait for the
@@ -3252,8 +3250,8 @@ __perf_counter_exit_task(struct task_struct *child,
*/
if (child != current) {
wait_task_inactive(child, 0);
- list_del_init(&child_counter->list_entry);
update_counter_times(child_counter);
+ list_del_counter(child_counter, child_ctx);
} else {
struct perf_cpu_context *cpuctx;
unsigned long flags;
@@ -3272,9 +3270,7 @@ __perf_counter_exit_task(struct task_struct *child,
group_sched_out(child_counter, cpuctx, child_ctx);
update_counter_times(child_counter);
- list_del_init(&child_counter->list_entry);
-
- child_ctx->nr_counters--;
+ list_del_counter(child_counter, child_ctx);
perf_enable();
local_irq_restore(flags);
@@ -3288,13 +3284,6 @@ __perf_counter_exit_task(struct task_struct *child,
*/
if (parent_counter) {
sync_child_counter(child_counter, parent_counter);
- list_for_each_entry_safe(sub, tmp, &child_counter->sibling_list,
- list_entry) {
- if (sub->parent) {
- sync_child_counter(sub, sub->parent);
- free_counter(sub);
- }
- }
free_counter(child_counter);
}
}
@@ -3315,9 +3304,18 @@ void perf_counter_exit_task(struct task_struct *child)
if (likely(!child_ctx->nr_counters))
return;
+again:
list_for_each_entry_safe(child_counter, tmp, &child_ctx->counter_list,
list_entry)
__perf_counter_exit_task(child, child_counter, child_ctx);
+
+ /*
+ * If the last counter was a group counter, it will have appended all
+ * its siblings to the list, but we obtained 'tmp' before that which
+ * will still point to the list head terminating the iteration.
+ */
+ if (!list_empty(&child_ctx->counter_list))
+ goto again;
}
/*
--
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