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set_task_comm: kill the pointless memset() + wmb()

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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>
This commit is contained in:
Oleg Nesterov
2013-04-30 15:28:19 -07:00
committed by Linus Torvalds
parent 830e0fc967
commit 12eaaf309a
1 changed files with 0 additions and 10 deletions
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10
fs/exec.c
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@@ -1027,17 +1027,7 @@ EXPORT_SYMBOL_GPL(get_task_comm);
void set_task_comm(struct task_struct *tsk, char *buf) void set_task_comm(struct task_struct *tsk, char *buf)
{ {
task_lock(tsk); task_lock(tsk);
trace_task_rename(tsk, buf); 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)); strlcpy(tsk->comm, buf, sizeof(tsk->comm));
task_unlock(tsk); task_unlock(tsk);
perf_event_comm(tsk); perf_event_comm(tsk);