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path: root/Documentation/power/freezing-of-tasks.txt
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2011-11-21freezer: unexport refrigerator() and update try_to_freeze() slightlyTejun Heo
There is no reason to export two functions for entering the refrigerator. Calling refrigerator() instead of try_to_freeze() doesn't save anything noticeable or removes any race condition. * Rename refrigerator() to __refrigerator() and make it return bool indicating whether it scheduled out for freezing. * Update try_to_freeze() to return bool and relay the return value of __refrigerator() if freezing(). * Convert all refrigerator() users to try_to_freeze(). * Update documentation accordingly. * While at it, add might_sleep() to try_to_freeze(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Samuel Ortiz <samuel@sortiz.org> Cc: Chris Mason <chris.mason@oracle.com> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Jan Kara <jack@suse.cz> Cc: KONISHI Ryusuke <konishi.ryusuke@lab.ntt.co.jp> Cc: Christoph Hellwig <hch@infradead.org>
2011-11-21freezer: don't unnecessarily set PF_NOFREEZE explicitlyTejun Heo
Some drivers set PF_NOFREEZE in their kthread functions which is completely unnecessary and racy - some part of freezer code doesn't consider cases where PF_NOFREEZE is set asynchronous to freezer operations. In general, there's no reason to allow setting PF_NOFREEZE explicitly. Remove them and change the documentation to note that setting PF_NOFREEZE directly isn't allowed. -v2: Dropped change to twl4030-irq.c as it no longer uses PF_NOFREEZE. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: "Gustavo F. Padovan" <padovan@profusion.mobi> Acked-by: Samuel Ortiz <sameo@linux.intel.com> Cc: Marcel Holtmann <marcel@holtmann.org> Cc: wwang <wei_wang@realsil.com.cn>
2011-11-04PM / Sleep: Update freezer documentationSrivatsa S. Bhat
This patch: * Substitutes some obsolete references to kernel/power/process.c by kernel/freezer.c. * Mentions kernel/freezer.c as being part of the "freezer" code along with the rest of the files. * Fixes a trivial typo. Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
2007-10-18freezer: do not send signals to kernel threadsRafael J. Wysocki
The freezer should not send signals to kernel threads, since that may lead to subtle problems. In particular, commit b74d0deb968e1f85942f17080eace015ce3c332c has changed recalc_sigpending_tsk() so that it doesn't clear TIF_SIGPENDING. For this reason, if the freezer continues to send fake signals to kernel threads and the freezing of kernel threads fails, some of them may be running with TIF_SIGPENDING set forever. Accordingly, recalc_sigpending_tsk() shouldn't set the task's TIF_SIGPENDING flag if TIF_FREEZE is set. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Cc: Nigel Cunningham <nigel@nigel.suspend2.net> Cc: Pavel Machek <pavel@ucw.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-18freezer: document relationship with memory shrinkingRafael J. Wysocki
One important reason to freeze tasks, which is that we don't want them to allocate memory after freeing it for the hibernation image, has not been documented. Fix it. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Pavel Machek <pavel@ucw.cz> Acked-by: Nigel Cunningham <nigel@nigel.suspend2.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-21Documentation:reference notifiers.txt in freezing-of-tasks.txtOliver Neukum
freezing-of-tasks.txt mentions firmware issues without mentioning the use of the new notifier API to overcome them. Here's an update. Signed-off-by: Oliver Neukum <oneukum@suse.de> Acked-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Nigel Cunningham <nigel@nigel.suspend2.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-17Freezer: make kernel threads nonfreezable by defaultRafael J. Wysocki
Currently, the freezer treats all tasks as freezable, except for the kernel threads that explicitly set the PF_NOFREEZE flag for themselves. This approach is problematic, since it requires every kernel thread to either set PF_NOFREEZE explicitly, or call try_to_freeze(), even if it doesn't care for the freezing of tasks at all. It seems better to only require the kernel threads that want to or need to be frozen to use some freezer-related code and to remove any freezer-related code from the other (nonfreezable) kernel threads, which is done in this patch. The patch causes all kernel threads to be nonfreezable by default (ie. to have PF_NOFREEZE set by default) and introduces the set_freezable() function that should be called by the freezable kernel threads in order to unset PF_NOFREEZE. It also makes all of the currently freezable kernel threads call set_freezable(), so it shouldn't cause any (intentional) change of behaviour to appear. Additionally, it updates documentation to describe the freezing of tasks more accurately. [akpm@linux-foundation.org: build fixes] Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Nigel Cunningham <nigel@nigel.suspend2.net> Cc: Pavel Machek <pavel@ucw.cz> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: Gautham R Shenoy <ego@in.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>