On 11/7/06, Alasdair G Kergon <[email protected]> wrote:
From: Srinivasa Ds <[email protected]>
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 it.
Srinivasa's description of the patch just speaks to how freeze_bdev
and thaw_bdev are used by DM but completely skips justification for
switching from mutex to semaphore. Why is it beneficial and/or
necessary to use a semaphore instead of a mutex here?
Mike
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