From: Christophe Lyon <christophe.lyon@linaro.org>
To: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Cc: gdb-patches@sourceware.org
Subject: Re: [RFC PATCH 0/3] Fix attaching to process when it has zombie threads
Date: Fri, 22 Mar 2024 11:17:17 +0100 [thread overview]
Message-ID: <CAPS5khZ09sDyzVVEAdt9-FFm2CN1mA4yFrGDRJk=OS+ih8tG6Q@mail.gmail.com> (raw)
In-Reply-To: <20240321231149.519549-1-thiago.bauermann@linaro.org>
Hi!
On Fri, 22 Mar 2024 at 00:12, Thiago Jung Bauermann
<thiago.bauermann@linaro.org> wrote:
>
> Hello,
>
> This patch series fixes a GDB hang when attaching to a multi-threaded
> inferior which happens often (but not always) on aarch64-linux and
> powerpc64le-linux, as described in PR 31312. See patch 3 for a detailed
> descripiton of the problem.
>
> Patches 1 and 2 are preparatory patches because I want to use existing code
> to parse the /proc/PID/stat file to get the thread's starttime value, so
> that GDB and gdbserver aren't fooled by PID reuse.
>
> This patch series was tested on native and extended-remote aarch64-linux
> and armv8l-linux-gnueabihf and no regressions were found, except for the
> following:
>
> When running gdb.threads/detach-step-over.exp on armv8l-linux-gnueabihf
> extended-remote, sometimes GDBserver dies with:
>
> builtin_spawn /home/thiago.bauermann/.cache/builds/gdb-native-aarch32/gdb/testsuite/outputs/gdb.threads/detach-step-over/detach-step-over
> Remote debugging from host 127.0.0.1, port 56624
> Process /home/thiago.bauermann/.cache/builds/gdb-native-aarch32/gdb/testsuite/outputs/gdb.threads/detach-step-over/detach-step-over created; pid = 840876
> Attached; pid = 840821
> Detaching from process 840821
> Attached; pid = 840821
> /home/thiago.bauermann/src/binutils-gdb/gdbserver/linux-low.cc:1956: A problem internal to GDBserver has been detected.
> unsuspend LWP 840821, suspended=-1
>
> The assertion triggered is this one:
>
> /* Decrement LWP's suspend count. */
>
> static void
> lwp_suspended_decr (struct lwp_info *lwp)
> {
> lwp->suspended--;
>
> if (lwp->suspended < 0)
> {
> struct thread_info *thread = get_lwp_thread (lwp);
>
> internal_error ("unsuspend LWP %ld, suspended=%d\n", lwpid_of (thread),
> lwp->suspended);
> }
> }
>
> Unfortunately for the moment I don't have time to further debug this
> problem and I didn't want to keep sitting on these patches until I can come
> back to this issue.
>
> Note that of all the testcases in the GDB testsuite, only
> detach-step-over.exp triggers the GDBserver internal error so it's a
> localized problem.
>
> This is why I'm posting the patch series as an RFC. Considering that it
> fixes a problem that is causing instability in the testsuite results for
> aarch64-linux and powerpc64le-linux, does it make sense to commit it as is,
> and then investigate the GDBserver internal error on armv8l-linux-gnueabihf
> later?
I quickly looked at the series, patches 1 and 2 LGTM, I would say
patch 3 too, but it seems to be causing the random failures you
mention :-(
However, I think your rationale is OK, trading many failures for a
single, localized one.
But of course, I'm not a maintainer :-)
Thanks,
Christophe
>
> Thiago Jung Bauermann (3):
> gdb/nat: Use procfs(5) indexes in linux_common_core_of_thread
> gdb/nat: Factor linux_find_proc_stat_field out of
> linux_common_core_of_thread
> gdb/nat/linux: Fix attaching to process when it has zombie threads
>
> gdb/nat/linux-osdata.c | 65 +++++++++++++++++++++++++++++++++---------
> gdb/nat/linux-osdata.h | 7 +++++
> gdb/nat/linux-procfs.c | 19 ++++++++++++
> 3 files changed, 77 insertions(+), 14 deletions(-)
>
>
> base-commit: b42aa684f6ff2bce9b8bc58aa89574723f17f1ce
prev parent reply other threads:[~2024-03-22 10:18 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-21 23:11 Thiago Jung Bauermann
2024-03-21 23:11 ` [RFC PATCH 1/3] gdb/nat: Use procfs(5) indexes in linux_common_core_of_thread Thiago Jung Bauermann
2024-03-22 17:33 ` Luis Machado
2024-04-17 15:55 ` Pedro Alves
2024-04-20 5:15 ` Thiago Jung Bauermann
2024-03-21 23:11 ` [RFC PATCH 2/3] gdb/nat: Factor linux_find_proc_stat_field out of linux_common_core_of_thread Thiago Jung Bauermann
2024-03-22 16:12 ` Luis Machado
2024-04-17 16:06 ` Pedro Alves
2024-04-20 5:16 ` Thiago Jung Bauermann
2024-03-21 23:11 ` [RFC PATCH 3/3] gdb/nat/linux: Fix attaching to process when it has zombie threads Thiago Jung Bauermann
2024-03-22 16:19 ` Luis Machado
2024-03-22 16:52 ` Pedro Alves
2024-04-16 4:48 ` Thiago Jung Bauermann
2024-04-17 15:32 ` Pedro Alves
2024-04-20 5:00 ` Thiago Jung Bauermann
2024-04-26 15:35 ` Pedro Alves
2024-04-17 16:28 ` Pedro Alves
2024-04-20 5:28 ` Thiago Jung Bauermann
2024-03-22 10:17 ` Christophe Lyon [this message]
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