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SubjectRe: fastboot/async and initramfs: How am I supposed to know when devices are finished initializing?
From
On Sun, Mar 29, 2009 at 11:06 AM, Kay Sievers <kay.sievers@vrfy.org> wrote:
> Assembling meta devices, or multi-volume devices should be triggered
> directly when the underlying devices show up. If auto-assembly (which
> kind of works today with md's --incremental) is properly implemented,
> you should still be able to just wait for the specified root device to
> show up...

Incremental assembly mostly works but it would be nice to have some
event to signal "proceed with degraded assembly because I do not think
any more disks are coming". With the below patch my thought is that
we can have a rule that:
1/ checks if incremental assembly is in progress (to prevent adding
timeouts to the non-raid path)
2/ checks if the udev event queue is empty
3/ upon finding an idle queue pause to allow last chance discovery
4/ assuming the queue remains idle proceed with degraded assembly

Thoughts? Perhaps (3) can be eliminated after loading scsi_wait_scan.

Thanks,
Dan

---ws damaged patch---
settle: allow --timeout=0 to test for "queue busy"

From: Dan Williams <dan.j.williams@intel.com>

Allow udevadm settle to be used as a "queue busy" detector. For use in
a early raid discovery where we want to hold off committing to the
current list of disks while devices might still be arriving.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
udev/udevadm-settle.c | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/udev/udevadm-settle.c b/udev/udevadm-settle.c
index 867bbed..2fa85a4 100644
--- a/udev/udevadm-settle.c
+++ b/udev/udevadm-settle.c
@@ -85,6 +85,9 @@ int udevadm_settle(struct udev *udev, int argc, char *argv[])
usleep(1000 * 1000 / LOOP_PER_SECOND);
}

+ if (!udev_queue_get_queue_is_empty(udev_queue))
+ rc = 1;
+
/* if we reached the timeout, print the list of remaining events */
if (loop <= 0) {
struct udev_list_entry *list_entry;
@@ -97,7 +100,6 @@ int udevadm_settle(struct udev *udev, int argc, char *argv[])
udev_list_entry_get_name(list_entry),
udev_list_entry_get_value(list_entry));
}
- rc = 1;
}
exit:
udev_queue_unref(udev_queue);

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