lvcreate - race condition creating snapshots

I think, there is a race condition in lvcreate while makeing a new snapshot.

System: Tyan with 2 Opteron 246

        xen 3.0.2-3
        linux 2.6.16.13
        lvm 2.02.07
        3ware-Raid 9550 Raid5

Under xen i was unable to create a snapshot, I got always "LV system/snap in use: not deactivating". Without xen, i got occasionally a snapshot.

After i make a "dirty hack":
------ begin ----------
*** old/lvcreate.c 2006-06-10 19:22:37.000000000 +0200
--- lvcreate.c 2006-06-10 19:23:04.000000000 +0200
***************
*** 776,781 ****
--- 776,787 ----

                /* Reset permission after zeroing */
                if (!(lp->permission & LVM_WRITE))
                        lv->status &= ~LVM_WRITE;
+
+                 { struct timeval tv ;
+                   tv.tv_sec=10;
+                   tv.tv_usec=0;
+                   select(2, 0, 0, 0, &tv);
+                 }
                if (!deactivate_lv(cmd, lv)) {
                        log_err("Couldn't deactivate new snapshot.");
                        return 0;

------ end ---------

i got always a snapshot (on all 3 systems!). I think, there is an other thread which is creating the new lv, and it will take longer as the lvcreate will "think". I have to less knowledge to make a patch, which is waiting for the correct event (creating lv complete).

regards
Robert Valentan

<..>

Are you running udev, perchance?

Try reading the thread entitled "Problem creating snapshots with 2.6.16.9 and LVM 2.02.06", and refer to the following Debian bug:

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=343671

In the bug history, there's debate if it's a problem with LVM or udev, although your mail seems to indicate LVM. :)

(Note that I've also been having this problem for awhile, and the udev "hack" seems to resolve it..)

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| nate carlson | [email protected] | http://www.natecarlson.com |
|       depriving some poor village of its idiot since 1981            |

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