set_task_comm: kill the pointless memset() + wmb()
set_task_comm() does memset() + wmb() before strlcpy(). This buys
nothing and to add to the confusion, the comment is wrong.
- We do not need memset() to be "safe from non-terminating string
reads", the final char is always zero and we never change it.
- wmb() is paired with nothing, it cannot prevent from printing
the mixture of the old/new data unless the reader takes the lock.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/exec.c b/fs/exec.c
index 87e731f..260f89f 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1027,17 +1027,7 @@
void set_task_comm(struct task_struct *tsk, char *buf)
{
task_lock(tsk);
-
trace_task_rename(tsk, buf);
-
- /*
- * Threads may access current->comm without holding
- * the task lock, so write the string carefully.
- * Readers without a lock may see incomplete new
- * names but are safe from non-terminating string reads.
- */
- memset(tsk->comm, 0, TASK_COMM_LEN);
- wmb();
strlcpy(tsk->comm, buf, sizeof(tsk->comm));
task_unlock(tsk);
perf_event_comm(tsk);