Attachment 100504 Details for Bug 79576 – handle preexisting flocks in udevd.c

handle preexisting flocks in udevd.c

05-systemd-213-udev-accommodate.existing.flocks.patch (text/plain), 3.48 KB, created by jpsinthemix on 2014-06-06 06:08:34 UTC

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Creator: jpsinthemix

Created: 2014-06-06 06:08:34 UTC

Size: 3.48 KB

patch

obsolete

>--- systemd-213.old/src/udev/udevd.c	2014-06-06 01:09:22.464595897 -0400
>+++ systemd-213.new/src/udev/udevd.c	2014-06-06 01:18:04.499589005 -0400
>@@ -297,13 +297,30 @@ static void worker_new(struct event *eve
>                                         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;
>-                                                fd_lock = safe_close(fd_lock);
>-                                                goto skip;
>+                                        /*
>+                                         * to accommodate cases where other prcoesses may already hold an
>+                                         * incompatible flock (LOCK_EX), allow up to approximately 8 seconds
>+                                         * (in 250 ms increments) to acquire an flock
>+                                         */
>+                                        int fl_err, fl_tries = 32, fl_try_us = 250000;
>+                                        if ((fd_lock=open(udev_device_get_devnode(d),
>+                                             O_RDONLY|O_CLOEXEC|O_NOFOLLOW|O_NONBLOCK)) >= 0) {
>+
>+                                                while ((fl_err=flock(fd_lock, LOCK_SH|LOCK_NB)) && --fl_tries) {
>+                                                        log_debug("Unable to flock(%s[%s]); %d tries remaining: %m",
>+                                                                  udev_device_get_devnode(d), udev_device_get_devnode(dev),
>+                                                                  fl_tries);
>+                                                        usleep(fl_try_us);
>+                                                }
>+                                                if (fl_err) {
>+                                                        log_error("Unable to flock(%s[%s]); skipping event handling: %m",
>+                                                                  udev_device_get_devnode(d), udev_device_get_devnode(dev));
>+                                                        err = -EWOULDBLOCK;
>+                                                        safe_close(fd_lock);
>+                                                        goto skip;
>+                                                }
>                                         }
>+                                        /* handle open failures? */
>                                 }
>                         }
> 
>@@ -318,6 +335,14 @@ static void worker_new(struct event *eve
>                                 udev_device_update_db(dev);
>                         }
> 
>+                        /*
>+                         * explicitly unlock in case there are other open file descriptors
>+                         * on the device; closing will only unlock the file after all such
>+                         * descriptors are closed
>+                         */
>+                        if (fd_lock >= 0)
>+                                flock(fd_lock, LOCK_UN);
>+
>                         safe_close(fd_lock);
> 
>                         /* send processed event back to libudev listeners */

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Attachments on bug 79576: 100341 | 100504

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