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Wed, 02 Feb 2022 16:28:47 +0000 X-MC-Unique: EWZNk6tXMLqpX5tzD7Vuaw-1 X-MC-Unique: Byd-sA2vOeSn46biXvsI0A-1 From: Vasiliy Ulyanov To: libvir-list@redhat.com Subject: [PATCH v3 1/3] virpidfile: Add virPidFileReadPathIfLocked func Date: Wed, 2 Feb 2022 17:28:15 +0100 Message-Id: <20220202162817.16258-2-vulyanov@suse.de> In-Reply-To: <20220202162817.16258-1-vulyanov@suse.de> References: <20220202162817.16258-1-vulyanov@suse.de> MIME-Version: 1.0 X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 X-MIME-Autoconverted: from quoted-printable to 8bit by lists01.pubmisc.prod.ext.phx2.redhat.com id 212GSok4021949 X-loop: libvir-list@redhat.com X-BeenThere: libvir-list@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: Development discussions about the libvirt library & tools List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: libvir-list-bounces@redhat.com Errors-To: libvir-list-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=libvir-list-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable X-ZM-MESSAGEID: 1643819346540100001 Content-Type: text/plain; charset="utf-8" The function will attempt to read a pid from @path, and store it in @pid. The @pid will only be set, however, if @path is locked by virFileLock() at byte 0 and the pid in @path is running. Signed-off-by: Vasiliy Ulyanov --- src/libvirt_private.syms | 1 + src/util/virpidfile.c | 34 ++++++++++++++++++++++++++++++++++ src/util/virpidfile.h | 2 ++ 3 files changed, 37 insertions(+) diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms index 9bc3d9530b..447ba9d82b 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -3070,6 +3070,7 @@ virPidFileRead; virPidFileReadIfAlive; virPidFileReadPath; virPidFileReadPathIfAlive; +virPidFileReadPathIfLocked; virPidFileRelease; virPidFileReleasePath; virPidFileWrite; diff --git a/src/util/virpidfile.c b/src/util/virpidfile.c index 7069f8343d..b8bb455e5e 100644 --- a/src/util/virpidfile.c +++ b/src/util/virpidfile.c @@ -302,6 +302,40 @@ int virPidFileReadIfAlive(const char *dir, return 0; } =20 +/** + * virPidFileReadPathIfLocked: + * @path: path to pidfile + * @pid: variable to return pid in + * + * This will attempt to read a pid from @path, and store it + * in @pid. The @pid will only be set, however, if the + * pid in @path is running, and @path is locked by virFileLock() + * at byte 0. This adds protection against returning a stale pid. + * + * Returns -1 upon error, or zero on successful + * reading of the pidfile. If @path is not locked + * or if the PID was not still alive, zero will + * be returned, but @pid will be set to -1. + */ +int virPidFileReadPathIfLocked(const char *path, pid_t *pid) +{ + VIR_AUTOCLOSE fd =3D -1; + + if ((fd =3D open(path, O_RDWR)) < 0) + return -1; + + if (virFileLock(fd, false, 0, 1, false) >=3D 0) { + /* The file isn't locked. PID is stale. */ + *pid =3D -1; + return 0; + } + + if (virPidFileReadPathIfAlive(path, pid, NULL) < 0) + return -1; + + return 0; +} + =20 int virPidFileDeletePath(const char *pidfile) { diff --git a/src/util/virpidfile.h b/src/util/virpidfile.h index fd8013c41e..e84542f298 100644 --- a/src/util/virpidfile.h +++ b/src/util/virpidfile.h @@ -48,6 +48,8 @@ int virPidFileReadIfAlive(const char *dir, const char *name, pid_t *pid, const char *binpath) G_GNUC_WARN_UNUSED_RESULT; +int virPidFileReadPathIfLocked(const char *path, + pid_t *pid) G_GNUC_WARN_UNUSED_RESULT; =20 int virPidFileDeletePath(const char *path); int virPidFileDelete(const char *dir, --=20 2.34.1