perf events: Split out task search into helper

Split out the code which searches for non-exiting tasks into its own
helper. Creating this helper not only makes the code slightly more
readable it prepares to move the search out of find_get_context() in
a subsequent commit.

Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Robin Green <greenrd@greenrd.org>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
LKML-Reference: <561205417b450b8a4bf7488374541d64b4690431.1284407762.git.matthltc@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 40 insertions, 23 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 440f9ca067b2..3f5309db72f1 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -2015,6 +2015,43 @@ alloc_perf_context(struct pmu *pmu, struct task_struct *task)
         return ctx;
 }
 
+static struct task_struct *
+find_lively_task_by_vpid(pid_t vpid)
+{
+        struct task_struct *task;
+        int err;
+
+        rcu_read_lock();
+        if (!vpid)
+                task = current;
+        else
+                task = find_task_by_vpid(vpid);
+        if (task)
+                get_task_struct(task);
+        rcu_read_unlock();
+
+        if (!task)
+                return ERR_PTR(-ESRCH);
+
+        /*
+         * Can't attach events to a dying task.
+         */
+        err = -ESRCH;
+        if (task->flags & PF_EXITING)
+                goto errout;
+
+        /* Reuse ptrace permission checks for now. */
+        err = -EACCES;
+        if (!ptrace_may_access(task, PTRACE_MODE_READ))
+                goto errout;
+
+        return task;
+errout:
+        put_task_struct(task);
+        return ERR_PTR(err);
+
+}
+
 static struct perf_event_context *
 find_get_context(struct pmu *pmu, pid_t pid, int cpu)
 {
@@ -2047,29 +2084,9 @@ find_get_context(struct pmu *pmu, pid_t pid, int cpu)
                 return ctx;
         }
 
-        rcu_read_lock();
-        if (!pid)
-                task = current;
-        else
-                task = find_task_by_vpid(pid);
-        if (task)
-                get_task_struct(task);
-        rcu_read_unlock();
-
-        if (!task)
-                return ERR_PTR(-ESRCH);
-
-        /*
-         * Can't attach events to a dying task.
-         */
-        err = -ESRCH;
-        if (task->flags & PF_EXITING)
-                goto errout;
-
-        /* Reuse ptrace permission checks for now. */
-        err = -EACCES;
-        if (!ptrace_may_access(task, PTRACE_MODE_READ))
-                goto errout;
+        task = find_lively_task_by_vpid(pid);
+        if (IS_ERR(task))
+                return (void*)task;
 
         err = -EINVAL;
         ctxn = pmu->task_ctx_nr;