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Subject[PATCH 4/5] perf_counter: propagate inheritance failures down the fork() path
Fail fork() when we fail inheritance for some reason (-ENOMEM most likely).

LKML-Reference: <new-submission>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
kernel/fork.c | 5 ++++-
kernel/perf_counter.c | 20 ++++++++++++--------
2 files changed, 16 insertions(+), 9 deletions(-)
Index: linux-2.6/kernel/fork.c
===================================================================
--- linux-2.6.orig/kernel/fork.c
+++ linux-2.6/kernel/fork.c
@@ -983,7 +983,9 @@ static struct task_struct *copy_process(
goto fork_out;

rt_mutex_init_task(p);
- perf_counter_init_task(p);
+ retval = perf_counter_init_task(p);
+ if (retval)
+ goto bad_fork_free;

#ifdef CONFIG_PROVE_LOCKING
DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
@@ -1309,6 +1311,7 @@ bad_fork_cleanup_count:
put_cred(p->real_cred);
put_cred(p->cred);
bad_fork_free:
+ perf_counter_exit_task(p);
free_task(p);
fork_out:
return ERR_PTR(retval);
Index: linux-2.6/kernel/perf_counter.c
===================================================================
--- linux-2.6.orig/kernel/perf_counter.c
+++ linux-2.6/kernel/perf_counter.c
@@ -3434,18 +3434,23 @@ again:
/*
* Initialize the perf_counter context in task_struct
*/
-void perf_counter_init_task(struct task_struct *child)
+int perf_counter_init_task(struct task_struct *child)
{
struct perf_counter_context *child_ctx, *parent_ctx;
struct perf_counter *counter;
struct task_struct *parent = current;
int inherited_all = 1;
+ int ret = 0;

child->perf_counter_ctxp = NULL;

mutex_init(&child->perf_counter_mutex);
INIT_LIST_HEAD(&child->perf_counter_list);

+ parent_ctx = parent->perf_counter_ctxp;
+ if (likely(!parent_ctx || !parent_ctx->nr_counters))
+ return 0;
+
/*
* This is executed from the parent task context, so inherit
* counters that have been marked for cloning.
@@ -3454,11 +3459,7 @@ void perf_counter_init_task(struct task_

child_ctx = kmalloc(sizeof(struct perf_counter_context), GFP_KERNEL);
if (!child_ctx)
- return;
-
- parent_ctx = parent->perf_counter_ctxp;
- if (likely(!parent_ctx || !parent_ctx->nr_counters))
- return;
+ return -ENOMEM;

__perf_counter_init_context(child_ctx, child);
child->perf_counter_ctxp = child_ctx;
@@ -3482,8 +3483,9 @@ void perf_counter_init_task(struct task_
continue;
}

- if (inherit_group(counter, parent,
- parent_ctx, child, child_ctx)) {
+ ret = inherit_group(counter, parent, parent_ctx,
+ child, child_ctx);
+ if (ret) {
inherited_all = 0;
break;
}
@@ -3505,6 +3507,8 @@ void perf_counter_init_task(struct task_
}

mutex_unlock(&parent_ctx->mutex);
+
+ return ret;
}

static void __cpuinit perf_counter_init_cpu(int cpu)
--



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