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Mon, 6 Mar 2023 15:29:26 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.193.92]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D32E7492C3E; Mon, 6 Mar 2023 15:29:25 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id B661421E6A1F; Mon, 6 Mar 2023 16:29:24 +0100 (CET) From: Markus Armbruster To: marcandre.lureau@redhat.com Cc: qemu-devel@nongnu.org, Thomas Huth , Gerd Hoffmann , Alex =?utf-8?Q?Benn=C3=A9e?= , Michael Roth , Paolo Bonzini , Laurent Vivier , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Beraldo Leal , Wainer dos Santos Moschetta , Stefan Weil , Daniel P. =?utf-8?Q?Berrang=C3=A9?= , Eric Blake , "Dr. David Alan Gilbert" Subject: Re: [PATCH v4 06/11] monitor: release the lock before calling close() References: <20230306122751.2355515-1-marcandre.lureau@redhat.com> <20230306122751.2355515-7-marcandre.lureau@redhat.com> Date: Mon, 06 Mar 2023 16:29:24 +0100 In-Reply-To: <20230306122751.2355515-7-marcandre.lureau@redhat.com> (marcandre lureau's message of "Mon, 6 Mar 2023 16:27:46 +0400") Message-ID: <87v8jdj3u3.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org marcandre.lureau@redhat.com writes: > From: Marc-Andr=C3=A9 Lureau > > As per comment, presumably to avoid syscall in critical section. > > Fixes: 0210c3b39bef08 ("monitor: Use LOCK_GUARD macros") > Signed-off-by: Marc-Andr=C3=A9 Lureau > Reviewed-by: Philippe Mathieu-Daud=C3=A9 > --- > monitor/fds.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/monitor/fds.c b/monitor/fds.c > index 26b39a0ce6..7daf1064e1 100644 > --- a/monitor/fds.c > +++ b/monitor/fds.c > @@ -80,7 +80,8 @@ void qmp_getfd(const char *fdname, Error **errp) > return; > } >=20=20 > - QEMU_LOCK_GUARD(&cur_mon->mon_lock); > + /* See close() call below. */ > + qemu_mutex_lock(&cur_mon->mon_lock); > QLIST_FOREACH(monfd, &cur_mon->fds, next) { > if (strcmp(monfd->name, fdname) !=3D 0) { > continue; > @@ -88,6 +89,7 @@ void qmp_getfd(const char *fdname, Error **errp) >=20=20 > tmp_fd =3D monfd->fd; > monfd->fd =3D fd; > + qemu_mutex_unlock(&cur_mon->mon_lock); > /* Make sure close() is outside critical section */ > close(tmp_fd); > return; Not changed by your patch, but odd: when no fd named @fdname exists, the command does nothing silently. Shouldn't it fail then? > @@ -98,6 +100,7 @@ void qmp_getfd(const char *fdname, Error **errp) > monfd->fd =3D fd; >=20=20 > QLIST_INSERT_HEAD(&cur_mon->fds, monfd, next); > + qemu_mutex_unlock(&cur_mon->mon_lock); > } >=20=20 > void qmp_closefd(const char *fdname, Error **errp) Alex suggested a different way to do this in reply to v3 of this patch. Please have a look and reply there.