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Thu, 2 Mar 2023 09:44:05 +0000 (GMT) References: <20230207142535.1153722-1-marcandre.lureau@redhat.com> <20230207142535.1153722-7-marcandre.lureau@redhat.com> User-agent: mu4e 1.9.21; emacs 29.0.60 From: Alex =?utf-8?Q?Benn=C3=A9e?= To: marcandre.lureau@redhat.com Cc: qemu-devel@nongnu.org, Beraldo Leal , Eric Blake , Stefan Weil , Paolo Bonzini , Laurent Vivier , "Dr. David Alan Gilbert" , Gerd Hoffmann , Michael Roth , Philippe =?utf-8?Q?Mathieu-Daud?= =?utf-8?Q?=C3=A9?= , Markus Armbruster , =?utf-8?Q?Dan?= =?utf-8?Q?iel_P=2E_Berrang=C3=A9?= , Thomas Huth , Wainer dos Santos Moschetta Subject: Re: [PATCH v3 06/10] monitor: release the lock before calling close() Date: Thu, 02 Mar 2023 09:34:15 +0000 In-reply-to: <20230207142535.1153722-7-marcandre.lureau@redhat.com> Message-ID: <87ttz3bi8q.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=2a00:1450:4864:20::32f; envelope-from=alex.bennee@linaro.org; helo=mail-wm1-x32f.google.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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, 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 I know this is already merged but as an academic exercise we could have kept the lock guard with a little restructuring like this: void qmp_closefd(const char *fdname, Error **errp) { Monitor *cur_mon =3D monitor_cur(); mon_fd_t *monfd; int tmp_fd =3D -1; WITH_QEMU_LOCK_GUARD(&cur_mon->mon_lock) { QLIST_FOREACH(monfd, &cur_mon->fds, next) { if (strcmp(monfd->name, fdname) !=3D 0) { continue; } QLIST_REMOVE(monfd, next); tmp_fd =3D monfd->fd; g_free(monfd->name); g_free(monfd); break; } } if (tmp_fd > 0) { /* close() must be outside critical section */ close(tmp_fd); } else { error_setg(errp, "File descriptor named '%s' not found", fdname); } } To my mind it makes it easier to reason about locking but I probably have an irrational aversion to multiple exit paths for locks. --=20 Alex Benn=C3=A9e Virtualisation Tech Lead @ Linaro