From: Tom de Vries <tdevries@suse.de>
To: Tom Tromey <tromey@adacore.com>, gdb-patches@sourceware.org
Cc: "Alexandra Hájková" <ahajkova@redhat.com>
Subject: Re: [PATCH] Re-acquire GIL earlier in gdbpy_parse_and_eval
Date: Fri, 28 Jul 2023 08:49:35 +0200 [thread overview]
Message-ID: <f8cb5d3b-c27b-4279-1ce8-03151608fd6a@suse.de> (raw)
In-Reply-To: <20230727135835.2450275-1-tromey@adacore.com>
On 7/27/23 15:58, Tom Tromey wrote:
> Tom de Vries filed a bug about an intermittent gdb DAP failure -- and
> coincidentally, at the same time, Alexandra Hájková sent email about a
> somewhat similar failure.
>
> After looking into this for a while (with no results) using ASan and
> valgrind, I found that setting PYTHONMALLOC=malloc_debug found the bug
> instantly.
>
> The problem is that gdbpy_parse_and_eval releases the GIL while
> calling parse_and_eval, but fails to re-acquire it before calling
> value_to_value_object. This is easily fixed by introducing a new
> scope.
>
Hi,
thanks for taking care of this.
I've tested this, and the PR no longer triggers for me.
[ FYI, I also tested for PR30680, both using the assert patch and tsan,
and that one still triggers. ]
Also, patch LGTM.
Tested-by: Tom de Vries <tdevries@suse.de>
Reviewed-By: Tom de Vries <tdevries@suse.de>
Thanks,
- Tom
> I wonder whether the test suite should unconditionally set
> PYTHONMALLOC=malloc_debug.
>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30686
> ---
> gdb/python/python.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/gdb/python/python.c b/gdb/python/python.c
> index 505fc4412d1..6a978d632e9 100644
> --- a/gdb/python/python.c
> +++ b/gdb/python/python.c
> @@ -994,9 +994,17 @@ gdbpy_parse_and_eval (PyObject *self, PyObject *args, PyObject *kw)
> PyObject *result = nullptr;
> try
> {
> - gdbpy_allow_threads allow_threads;
> scoped_value_mark free_values;
> - struct value *val = parse_and_eval (expr_str, flags);
> + struct value *val;
> + {
> + /* Allow other Python threads to run while we're evaluating
> + the expression. This is important because the expression
> + could involve inferior calls or otherwise be a lengthy
> + calculation. We take care here to re-acquire the GIL here
> + before continuing with Python work. */
> + gdbpy_allow_threads allow_threads;
> + val = parse_and_eval (expr_str, flags);
> + }
> result = value_to_value_object (val);
> }
> catch (const gdb_exception &except)
next prev parent reply other threads:[~2023-07-28 6:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-27 13:58 Tom Tromey
2023-07-28 6:49 ` Tom de Vries [this message]
2023-07-28 12:15 ` Tom Tromey
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