84 lines
3.6 KiB
Diff
84 lines
3.6 KiB
Diff
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From 3ebdb81ef088afd3b4c72b516beb5610f8c93a0d Mon Sep 17 00:00:00 2001
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From: Kay Sievers <kay@vrfy.org>
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Date: Sun, 13 Apr 2014 19:54:27 -0700
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Subject: [PATCH] udev: serialize/synchronize block device event handling with
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file locks
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---
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src/udev/udevd.c | 33 +++++++++++++++++++++++++++++++--
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1 file changed, 31 insertions(+), 2 deletions(-)
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diff --git src/udev/udevd.c src/udev/udevd.c
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index f9ee368..aecd208 100644
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--- src/udev/udevd.c
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+++ src/udev/udevd.c
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@@ -31,6 +31,7 @@
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#include <time.h>
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#include <getopt.h>
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#include <dirent.h>
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+#include <sys/file.h>
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#include <sys/time.h>
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#include <sys/prctl.h>
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#include <sys/socket.h>
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@@ -265,6 +266,7 @@ static void worker_new(struct event *event)
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for (;;) {
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struct udev_event *udev_event;
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struct worker_message msg;
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+ int fd_lock = -1;
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int err;
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log_debug("seq %llu running", udev_device_get_seqnum(dev));
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@@ -280,6 +282,30 @@ static void worker_new(struct event *event)
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if (exec_delay > 0)
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udev_event->exec_delay = exec_delay;
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+ /*
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+ * Take a "read lock" on the device node; this establishes
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+ * a concept of device "ownership" to serialize device
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+ * access. External processes holding a "write lock" will
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+ * cause udev to skip the event handling; in the case udev
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+ * acquired the lock, the external process will block until
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+ * udev has finished its event handling.
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+ */
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+ if (streq_ptr("block", udev_device_get_subsystem(dev))) {
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+ struct udev_device *d = dev;
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+
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+ if (streq_ptr("partition", udev_device_get_devtype(d)))
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+ d = udev_device_get_parent(d);
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+
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+ if (d) {
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+ fd_lock = open(udev_device_get_devnode(d), O_RDONLY|O_CLOEXEC|O_NOFOLLOW|O_NONBLOCK);
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+ if (fd_lock >= 0 && flock(fd_lock, LOCK_SH|LOCK_NB) < 0) {
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+ log_debug("Unable to flock(%s), skipping event handling: %m", udev_device_get_devnode(d));
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+ err = -EWOULDBLOCK;
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+ goto skip;
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+ }
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+ }
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+ }
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+
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/* apply rules, create node, symlinks */
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err = udev_event_execute_rules(udev_event, rules, &sigmask_orig);
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@@ -292,13 +318,16 @@ static void worker_new(struct event *event)
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udev_device_update_db(dev);
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}
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+ if (fd_lock >= 0)
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+ close(fd_lock);
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+
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/* send processed event back to libudev listeners */
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udev_monitor_send_device(worker_monitor, NULL, dev);
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+skip:
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/* send udevd the result of the event execution */
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memzero(&msg, sizeof(struct worker_message));
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- if (err != 0)
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- msg.exitcode = err;
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+ msg.exitcode = err;
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msg.pid = getpid();
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send(worker_watch[WRITE_END], &msg, sizeof(struct worker_message), 0);
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--
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1.7.9.2
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