On Thu, 2002-09-26 at 23:21, Shaya Potter wrote:
> asmlinkage long sys_getpid(void)
> {
> /* This is SMP safe - current->pid doesn't change */
> return current->tgid;
> }
>
> I assume we are returning tgid so that no matter what thread of a
> multithreaded program calls getpid we return the same value, and that
> the comment with pid is old and should have been updated when it was
> changed to return tgid. A student in my Operating Systems class pointed
> this out, so I figured no harm in pointing the possible bug out.
Yes, you are correct, the comment is wrong. We switched to returning
the tgid in early 2.4 when CLONE_THREAD was introduced. The tgid and
pid are identical unless CLONE_THREAD was used.
Attached patch fixes the typo and adds some comments explaining this.
Marcelo, patch is against 2.4.20-pre8, please apply.
Robert Love
--- linux-2.4.20-pre8/kernel/timer.c Thu Sep 26 23:37:02 2002
+++ linux/kernel/timer.c Thu Sep 26 23:39:25 2002
@@ -740,10 +740,18 @@
* The Alpha uses getxpid, getxuid, and getxgid instead. Maybe this
* should be moved into arch/i386 instead?
*/
-
+
+/**
+ * sys_getpid - return the thread group id of the current process
+ *
+ * Note, despite the name, this returns the tgid not the pid. The tgid and
+ * the pid are identical unless CLONE_THREAD was specified on clone() in
+ * which case the tgid is the same in all threads of the same group.
+ *
+ * This is SMP safe as current->tgid does not change.
+ */
asmlinkage long sys_getpid(void)
{
- /* This is SMP safe - current->pid doesn't change */
return current->tgid;
}
-
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This archive was generated by hypermail 2b29 : Mon Sep 30 2002 - 22:00:30 EST