[RFC][PATCH 1/7] perf: Fix task refcount issues

[Peter Zijlstra]

Currently it looks like find_lively_task_by_vpid() takes a task ref
and relies on find_get_context() to drop it.

The problem is that perf_event_create_kernel_counter() shouldn't be
dropping task refs.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Matt Helsley <matthltc@xxxxxxxxxx>
---
 kernel/perf_event.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Index: linux-2.6/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/kernel/perf_event.c
+++ linux-2.6/kernel/perf_event.c
@@ -2124,11 +2124,9 @@ find_get_context(struct pmu *pmu, struct
 		}
 	}
 
-	put_task_struct(task);
 	return ctx;
 
 errout:
-	put_task_struct(task);
 	return ERR_PTR(err);
 }
 
@@ -5536,7 +5534,7 @@ SYSCALL_DEFINE5(perf_event_open,
 	ctx = find_get_context(pmu, task, cpu);
 	if (IS_ERR(ctx)) {
 		err = PTR_ERR(ctx);
-		goto err_group_fd;
+		goto err_task;
 	}
 
 	/*
@@ -5632,6 +5630,9 @@ SYSCALL_DEFINE5(perf_event_open,
 
 err_context:
 	put_ctx(ctx);
+err_task:
+	if (task)
+		put_task_struct(task);
 err_group_fd:
 	fput_light(group_file, fput_needed);
 	free_event(event);


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