* [PATCH v2] Fix sporadic XFAILs in gdb.threads/attach-many-short-lived-threads.exp
@ 2024-04-06 4:46 Bernd Edlinger
2024-04-06 17:40 ` Andrew Burgess
0 siblings, 1 reply; 2+ messages in thread
From: Bernd Edlinger @ 2024-04-06 4:46 UTC (permalink / raw)
To: gdb-patches, Thiago Jung Bauermann
This is about random test failures like those:
XFAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 6: attach (EPERM)
XFAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 7: attach (EPERM)
XFAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 8: attach (EPERM)
XFAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 9: attach (EPERM)
XFAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 10: attach (EPERM)
The reason for this effect is apparently as follows:
There is a race condition when gdb tries to attach a thread but the
thread exits at the same time. Normally when that happens the return
code of ptrace(PTRACE_ATTACH, x) is EPERM, which could also have other
reasons. To detect the true reason, we try to open /proc/<pid>/status
which normally fails in that situation, but it may happen that the
fopen succeeds, and the thread disappears while reading the content,
then the read has the errno=ESRCH, use that as an indication that the
thread has exited between fopen and reading of the status file.
---
gdb/nat/linux-procfs.c | 11 +++--------
1 file changed, 3 insertions(+), 8 deletions(-)
v2: from kernel code review, it seems the missing "State:"
can only happen if the thread disappeared, so no need to
look at errno at all here.
diff --git a/gdb/nat/linux-procfs.c b/gdb/nat/linux-procfs.c
index e2086952ce6..8d46d5bf289 100644
--- a/gdb/nat/linux-procfs.c
+++ b/gdb/nat/linux-procfs.c
@@ -157,17 +157,12 @@ linux_proc_pid_is_gone (pid_t pid)
enum proc_state state;
have_state = linux_proc_pid_get_state (pid, 0, &state);
- if (have_state < 0)
+ if (have_state <= 0)
{
- /* If we can't open the status file, assume the thread has
- disappeared. */
+ /* If we can't open the status file or there is no "State:" line,
+ assume the thread has disappeared. */
return 1;
}
- else if (have_state == 0)
- {
- /* No "State:" line, assume thread is alive. */
- return 0;
- }
else
return (state == PROC_STATE_ZOMBIE || state == PROC_STATE_DEAD);
}
--
2.39.2
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH v2] Fix sporadic XFAILs in gdb.threads/attach-many-short-lived-threads.exp
2024-04-06 4:46 [PATCH v2] Fix sporadic XFAILs in gdb.threads/attach-many-short-lived-threads.exp Bernd Edlinger
@ 2024-04-06 17:40 ` Andrew Burgess
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Burgess @ 2024-04-06 17:40 UTC (permalink / raw)
To: Bernd Edlinger, gdb-patches, Thiago Jung Bauermann
Bernd Edlinger <bernd.edlinger@hotmail.de> writes:
Thanks for looking into these failures.
> This is about random test failures like those:
>
> XFAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 6: attach (EPERM)
> XFAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 7: attach (EPERM)
> XFAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 8: attach (EPERM)
> XFAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 9: attach (EPERM)
> XFAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 10: attach (EPERM)
>
> The reason for this effect is apparently as follows:
>
> There is a race condition when gdb tries to attach a thread but the
> thread exits at the same time. Normally when that happens the return
> code of ptrace(PTRACE_ATTACH, x) is EPERM, which could also have other
> reasons. To detect the true reason, we try to open /proc/<pid>/status
> which normally fails in that situation, but it may happen that the
> fopen succeeds, and the thread disappears while reading the content,
> then the read has the errno=ESRCH, use that as an indication that the
> thread has exited between fopen and reading of the status file.
I assume this would be the commit message for this change? This text
seems to be out of date given the changes in V2 and probably needs
updating.
Thanks,
Andrew
> ---
> gdb/nat/linux-procfs.c | 11 +++--------
> 1 file changed, 3 insertions(+), 8 deletions(-)
>
> v2: from kernel code review, it seems the missing "State:"
> can only happen if the thread disappeared, so no need to
> look at errno at all here.
>
> diff --git a/gdb/nat/linux-procfs.c b/gdb/nat/linux-procfs.c
> index e2086952ce6..8d46d5bf289 100644
> --- a/gdb/nat/linux-procfs.c
> +++ b/gdb/nat/linux-procfs.c
> @@ -157,17 +157,12 @@ linux_proc_pid_is_gone (pid_t pid)
> enum proc_state state;
>
> have_state = linux_proc_pid_get_state (pid, 0, &state);
> - if (have_state < 0)
> + if (have_state <= 0)
> {
> - /* If we can't open the status file, assume the thread has
> - disappeared. */
> + /* If we can't open the status file or there is no "State:" line,
> + assume the thread has disappeared. */
> return 1;
> }
> - else if (have_state == 0)
> - {
> - /* No "State:" line, assume thread is alive. */
> - return 0;
> - }
> else
> return (state == PROC_STATE_ZOMBIE || state == PROC_STATE_DEAD);
> }
> --
> 2.39.2
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2024-04-06 17:40 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2024-04-06 4:46 [PATCH v2] Fix sporadic XFAILs in gdb.threads/attach-many-short-lived-threads.exp Bernd Edlinger
2024-04-06 17:40 ` Andrew Burgess
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).