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Subject[tip:perfcounters/core] perf_counter: Ammend cleanup in fork() fail
Commit-ID:  bbbee90829304d156c12b171c0ac7e6e1aba8b90
Gitweb: http://git.kernel.org/tip/bbbee90829304d156c12b171c0ac7e6e1aba8b90
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Fri, 29 May 2009 14:25:58 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 29 May 2009 16:21:52 +0200

perf_counter: Ammend cleanup in fork() fail

When fork() fails we cannot use perf_counter_exit_task() since that
assumes to operate on current. Write a new helper that cleans up
unused/clean contexts.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
include/linux/perf_counter.h | 2 +
kernel/fork.c | 2 +-
kernel/perf_counter.c | 43 +++++++++++++++++++++++++++++++++++++++--
3 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 717bf3b..519a41b 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -579,6 +579,7 @@ extern void perf_counter_task_sched_out(struct task_struct *task,
extern void perf_counter_task_tick(struct task_struct *task, int cpu);
extern int perf_counter_init_task(struct task_struct *child);
extern void perf_counter_exit_task(struct task_struct *child);
+extern void perf_counter_free_task(struct task_struct *task);
extern void perf_counter_do_pending(void);
extern void perf_counter_print_debug(void);
extern void __perf_disable(void);
@@ -644,6 +645,7 @@ static inline void
perf_counter_task_tick(struct task_struct *task, int cpu) { }
static inline int perf_counter_init_task(struct task_struct *child) { return 0; }
static inline void perf_counter_exit_task(struct task_struct *child) { }
+static inline void perf_counter_free_task(struct task_struct *task) { }
static inline void perf_counter_do_pending(void) { }
static inline void perf_counter_print_debug(void) { }
static inline void perf_disable(void) { }
diff --git a/kernel/fork.c b/kernel/fork.c
index c07c333..23bf757 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1298,7 +1298,7 @@ bad_fork_cleanup_semundo:
bad_fork_cleanup_audit:
audit_free(p);
bad_fork_cleanup_policy:
- perf_counter_exit_task(p);
+ perf_counter_free_task(p);
#ifdef CONFIG_NUMA
mpol_put(p->mempolicy);
bad_fork_cleanup_cgroup:
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 0c000d3..79c3f26 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -3538,8 +3538,7 @@ static void sync_child_counter(struct perf_counter *child_counter,
}

static void
-__perf_counter_exit_task(struct task_struct *child,
- struct perf_counter *child_counter,
+__perf_counter_exit_task(struct perf_counter *child_counter,
struct perf_counter_context *child_ctx)
{
struct perf_counter *parent_counter;
@@ -3605,7 +3604,7 @@ void perf_counter_exit_task(struct task_struct *child)
again:
list_for_each_entry_safe(child_counter, tmp, &child_ctx->counter_list,
list_entry)
- __perf_counter_exit_task(child, child_counter, child_ctx);
+ __perf_counter_exit_task(child_counter, child_ctx);

/*
* If the last counter was a group counter, it will have appended all
@@ -3621,6 +3620,44 @@ again:
}

/*
+ * free an unexposed, unused context as created by inheritance by
+ * init_task below, used by fork() in case of fail.
+ */
+void perf_counter_free_task(struct task_struct *task)
+{
+ struct perf_counter_context *ctx = task->perf_counter_ctxp;
+ struct perf_counter *counter, *tmp;
+
+ if (!ctx)
+ return;
+
+ mutex_lock(&ctx->mutex);
+again:
+ list_for_each_entry_safe(counter, tmp, &ctx->counter_list, list_entry) {
+ struct perf_counter *parent = counter->parent;
+
+ if (WARN_ON_ONCE(!parent))
+ continue;
+
+ mutex_lock(&parent->child_mutex);
+ list_del_init(&counter->child_list);
+ mutex_unlock(&parent->child_mutex);
+
+ fput(parent->filp);
+
+ list_del_counter(counter, ctx);
+ free_counter(counter);
+ }
+
+ if (!list_empty(&ctx->counter_list))
+ goto again;
+
+ mutex_unlock(&ctx->mutex);
+
+ put_ctx(ctx);
+}
+
+/*
* Initialize the perf_counter context in task_struct
*/
int perf_counter_init_task(struct task_struct *child)

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