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From e55efa99fd829a4699aae6505e02fae7b50a40bc Mon Sep 17 00:00:00 2001
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From: Daniel Drake <drake@endlessm.com>
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Date: Mon, 6 Apr 2015 16:03:43 -0600
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Subject: [PATCH] udevd: fix synchronization with settle when handling inotify
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events
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udev uses inotify to implement a scheme where when the user closes
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a writable device node, a change uevent is forcefully generated.
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In the case of block devices, it actually requests a partition rescan.
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This currently can't be synchronized with "udevadm settle", i.e. this
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is not reliable in a script:
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sfdisk --change-id /dev/sda 1 81
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udevadm settle
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mount /dev/sda1 /foo
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The settle call doesn't synchronize there, so at the same time we try
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to mount the device, udevd is busy removing the partition device nodes and
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readding them again. The mount call often happens in that moment where the
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partition node has been removed but not readded yet.
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This exact issue was fixed long ago:
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http://git.kernel.org/cgit/linux/hotplug/udev.git/commit/?id=bb38678e3ccc02bcd970ccde3d8166a40edf92d3
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but that fix is no longer valid now that sequence numbers are no longer
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used.
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Fix this by forcing another mainloop iteration after handling inotify events
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before unblocking settle. If the inotify event caused us to generate a
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"change" event, we'll pick that up in the following loop iteration, before
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we reach the end of the loop where we respond to settle's control message,
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unblocking it.
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(cherry picked from commit 07ba8037bf2a2d6a683fa107ee6f2b9545fca23e)
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Cherry-picked from: 7a2e024
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Resolves: #1222517
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---
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src/udev/udevd.c | 15 ++++++++++++++-
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1 file changed, 14 insertions(+), 1 deletion(-)
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diff --git a/src/udev/udevd.c b/src/udev/udevd.c
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index e98c1fd..87a3f69 100644
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--- a/src/udev/udevd.c
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+++ b/src/udev/udevd.c
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@@ -1502,9 +1502,22 @@ int main(int argc, char *argv[]) {
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continue;
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/* device node watch */
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- if (is_inotify)
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+ if (is_inotify) {
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handle_inotify(udev);
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+ /*
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+ * settle might be waiting on us to determine the queue
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+ * state. If we just handled an inotify event, we might have
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+ * generated a "change" event, but we won't have queued up
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+ * the resultant uevent yet.
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+ *
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+ * Before we go ahead and potentially tell settle that the
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+ * queue is empty, lets loop one more time to update the
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+ * queue state again before deciding.
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+ */
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+ continue;
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+ }
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+
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/* tell settle that we are busy or idle, this needs to be before the
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* PING handling
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*/
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