[linux-lvm] Re: [RFC] Reverting "bd_mount_mutex" to "bd_mount_sem"
sandeen at sandeen.net
Fri Oct 6 20:50:12 UTC 2006
Ingo Molnar wrote:
> * Srinivasa Ds <srinivasa at in.ibm.com> wrote:
>> On debugging I found out that,"dmsetup suspend <device name>" calls
>> "freeze_bdev()",which locks "bd_mount_mutex" to make sure that no new
>> mounts happen on bdev until thaw_bdev() is called.
>> This "thaw_bdev()" is getting called when we resume the device
>> through "dmsetup resume <device-name>".
>> Hence we have 2 processes,one of which locks
>> "bd_mount_mutex"(dmsetup suspend) and Another(dmsetup resume) unlocks
> hm, to me this seems quite a fragile construct - even if the
> mutex-debugging warning is worked around by reverting to a semaphore.
Ingo, what do you feel is fragile about this? It seems like this is a
reasonable way to go, except that maybe a down_trylock would be good if
a 2nd process tries to freeze while it's already frozen...
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