diff options
| -rw-r--r-- | src/udev/udevd.c | 33 |
1 files changed, 31 insertions, 2 deletions
diff --git a/src/udev/udevd.c b/src/udev/udevd.c index f9ee36870b..aecd208d40 100644 --- a/src/udev/udevd.c +++ b/src/udev/udevd.c @@ -31,6 +31,7 @@ #include <time.h> #include <getopt.h> #include <dirent.h> +#include <sys/file.h> #include <sys/time.h> #include <sys/prctl.h> #include <sys/socket.h> @@ -265,6 +266,7 @@ static void worker_new(struct event *event) for (;;) { struct udev_event *udev_event; struct worker_message msg; + int fd_lock = -1; int err; log_debug("seq %llu running", udev_device_get_seqnum(dev)); @@ -280,6 +282,30 @@ static void worker_new(struct event *event) if (exec_delay > 0) udev_event->exec_delay = exec_delay; + /* + * Take a "read lock" on the device node; this establishes + * a concept of device "ownership" to serialize device + * access. External processes holding a "write lock" will + * cause udev to skip the event handling; in the case udev + * acquired the lock, the external process will block until + * udev has finished its event handling. + */ + if (streq_ptr("block", udev_device_get_subsystem(dev))) { + struct udev_device *d = dev; + + if (streq_ptr("partition", udev_device_get_devtype(d))) + d = udev_device_get_parent(d); + + if (d) { + fd_lock = open(udev_device_get_devnode(d), O_RDONLY|O_CLOEXEC|O_NOFOLLOW|O_NONBLOCK); + if (fd_lock >= 0 && flock(fd_lock, LOCK_SH|LOCK_NB) < 0) { + log_debug("Unable to flock(%s), skipping event handling: %m", udev_device_get_devnode(d)); + err = -EWOULDBLOCK; + goto skip; + } + } + } + /* apply rules, create node, symlinks */ err = udev_event_execute_rules(udev_event, rules, &sigmask_orig); @@ -292,13 +318,16 @@ static void worker_new(struct event *event) udev_device_update_db(dev); } + if (fd_lock >= 0) + close(fd_lock); + /* send processed event back to libudev listeners */ udev_monitor_send_device(worker_monitor, NULL, dev); +skip: /* send udevd the result of the event execution */ memzero(&msg, sizeof(struct worker_message)); - if (err != 0) - msg.exitcode = err; + msg.exitcode = err; msg.pid = getpid(); send(worker_watch[WRITE_END], &msg, sizeof(struct worker_message), 0); |