[Crash-utility] [PATCH v3 03/10] back_trace: don't check /proc if !LOCAL_ACTIVE()
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(a)redhat.com>
---
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