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PM / Hibernate: document open(/dev/snapshot) side effects

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Opening and closing /dev/snapshot causes the kernel to carry out
some hibernate preparations that should be documented.

[rjw: Added the changelog.]

Signed-off-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
This commit is contained in:
Pavel Machek 2010-04-23 20:32:29 +02:00 committed by Rafael J. Wysocki
parent c92445fadb
commit bc6a0cbd57
1 changed files with 4 additions and 0 deletions
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Documentation/power/userland-swsusp.txt
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@ -24,6 +24,10 @@ assumed to be in the resume mode. The device cannot be open for simultaneous
reading and writing. It is also impossible to have the device open more than reading and writing. It is also impossible to have the device open more than
once at a time. once at a time.
Even opening the device has side effects. Data structures are
allocated, and PM_HIBERNATION_PREPARE / PM_RESTORE_PREPARE chains are
called.
The ioctl() commands recognized by the device are: The ioctl() commands recognized by the device are:
SNAPSHOT_FREEZE - freeze user space processes (the current process is SNAPSHOT_FREEZE - freeze user space processes (the current process is