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udev-watch: retry to save watch handle with random delay
Also, remove the watch handle if we cannot save it.
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parent
20ec7d9ed5
commit
2d3af41f0e
@ -12,8 +12,13 @@
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#include "dirent-util.h"
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#include "fs-util.h"
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#include "parse-util.h"
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#include "random-util.h"
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#include "udev-watch.h"
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#define SAVE_WATCH_HANDLE_MAX_RETRIES 128
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#define MAX_RANDOM_DELAY (100 * USEC_PER_MSEC)
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#define MIN_RANDOM_DELAY ( 10 * USEC_PER_MSEC)
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int udev_watch_restore(int inotify_fd) {
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struct dirent *ent;
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DIR *dir;
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@ -93,11 +98,43 @@ int udev_watch_begin(int inotify_fd, sd_device *dev) {
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return ignore ? 0 : r;
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}
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r = device_set_watch_handle(dev, wd);
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if (r < 0)
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return log_device_warning_errno(dev, r, "Failed to save watch handle in /run/udev/watch: %m");
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for (unsigned i = 0; i < SAVE_WATCH_HANDLE_MAX_RETRIES; i++) {
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if (i > 0) {
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usec_t delay = MIN_RANDOM_DELAY + random_u64_range(MAX_RANDOM_DELAY - MIN_RANDOM_DELAY);
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return 0;
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/* When the same handle is reused for different device node, we may fail to
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* save the watch handle with -EEXIST. Let's consider the case of two workers A
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* and B do the following:
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*
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* 1. A calls inotify_rm_watch()
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* 2. B calls inotify_add_watch()
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* 3. B calls device_set_watch_handle()
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* 4. A calls device_set_watch_handle(-1)
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*
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* At step 3, the old symlinks to save the watch handle still exist. So,
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* device_set_watch_handle() fails with -EEXIST. */
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log_device_debug_errno(dev, r,
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"Failed to save watch handle '%i' for %s in "
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"/run/udev/watch, retrying in after %s: %m",
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wd, devnode, FORMAT_TIMESPAN(delay, USEC_PER_MSEC));
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(void) usleep(delay);
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}
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r = device_set_watch_handle(dev, wd);
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if (r >= 0)
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return 0;
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if (r != -EEXIST)
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break;
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}
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log_device_warning_errno(dev, r,
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"Failed to save watch handle '%i' for %s in /run/udev/watch: %m",
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wd, devnode);
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(void) inotify_rm_watch(inotify_fd, wd);
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return r;
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}
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int udev_watch_end(int inotify_fd, sd_device *dev) {
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