On 04/28, Dave Anderson wrote:
>
> > IOW. with the patch above the code actually does
> >
> > if (ACTIVE() && !INSTACK(...)) {
> > if (LOCAL_ACTIVE() && file_exists(...))
> > error("invalid/stale stack pointer");
> > else
> > error("task no longer exists\n");
> > }
> >
> > is it wrong?
> >
> > I thought that !INSTACK() here likely means the task has gone, but back_trace()
> > does the additional file_exists() to verify this, and "invalid/stale stack pointer"
> > error means that something was wrong.
> >
> > No?
>
> I can't even remember -- that code's been in place for so long I'd prefer to just
> leave it as-is, and for you to just add something like this:
>
> if (ACTIVE() && !INSTACK(esp, bt)) {
> + if (!(LOCAL_ACTIVE()) }
> + error(INFO, "whatever error message you'd like\n");
> + return;
> + }
OK.
-------------------------------------------------------------------------------
Subject: [PATCH v3 03/10] back_trace: don't check /proc if !LOCAL_ACTIVE()
Obviously the /proc/$tc->pid check can only make sense if LOCAL_ACTIVE().
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
kernel.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel.c b/kernel.c
index a6fa7a6..c82b854 100644
--- a/kernel.c
+++ b/kernel.c
@@ -2901,6 +2901,10 @@ back_trace(struct bt_info *bt)
}
if (ACTIVE() && !INSTACK(esp, bt)) {
+ if (!LOCAL_ACTIVE()) {
+ error(INFO, "task no longer exists\n");
+ return;
+ }
sprintf(buf, "/proc/%ld", bt->tc->pid);
if (!file_exists(buf, NULL))
error(INFO, "task no longer exists\n");
--
2.5.0
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