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authorRafael J. Wysocki <rjw@sisk.pl>2007-07-19 01:47:37 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-19 10:04:42 -0700
commitccd4b65aef4be2278543fde5b999e55a4d694fd8 (patch)
tree2753440a79dab444eb3fa01fcaed1c996e1cfe28 /kernel/power/process.c
parent8cdd4936c17bd8085cb0dfacc4a37ccf8d0ada7b (diff)
PM: prevent frozen user mode helpers from failing the freezing of tasks
At present, if a user mode helper is running while usermodehelper_pm_callback() is executed, the helper may be frozen and the completion in call_usermodehelper_exec() won't be completed until user space processes are thawed. As a result, the freezing of kernel threads may fail, which is not desirable. Prevent this from happening by introducing a counter of running user mode helpers and allowing usermodehelper_pm_callback() to succeed for action = PM_HIBERNATION_PREPARE or action = PM_SUSPEND_PREPARE only if there are no helpers running. [Namely, usermodehelper_pm_callback() waits for at most RUNNING_HELPERS_TIMEOUT for the number of running helpers to become zero and fails if that doesn't happen.] Special thanks to Uli Luckas <u.luckas@road.de>, Pavel Machek <pavel@ucw.cz> and Oleg Nesterov <oleg@tv-sign.ru> for reviewing the previous versions of this patch and for very useful comments. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Uli Luckas <u.luckas@road.de> Acked-by: Nigel Cunningham <nigel@nigel.suspend2.net> Acked-by: Pavel Machek <pavel@ucw.cz> Cc: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/power/process.c')
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