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Diffstat (limited to 'Documentation/power/kernel_threads.txt')
| -rw-r--r-- | Documentation/power/kernel_threads.txt | 40 |
1 files changed, 0 insertions, 40 deletions
diff --git a/Documentation/power/kernel_threads.txt b/Documentation/power/kernel_threads.txt deleted file mode 100644 index fb57784986b..00000000000 --- a/Documentation/power/kernel_threads.txt +++ /dev/null @@ -1,40 +0,0 @@ -KERNEL THREADS - - -Freezer - -Upon entering a suspended state the system will freeze all -tasks. This is done by delivering pseudosignals. This affects -kernel threads, too. To successfully freeze a kernel thread -the thread has to check for the pseudosignal and enter the -refrigerator. Code to do this looks like this: - - do { - hub_events(); - wait_event_interruptible(khubd_wait, !list_empty(&hub_event_list)); - try_to_freeze(); - } while (!signal_pending(current)); - -from drivers/usb/core/hub.c::hub_thread() - - -The Unfreezable - -Some kernel threads however, must not be frozen. The kernel must -be able to finish pending IO operations and later on be able to -write the memory image to disk. Kernel threads needed to do IO -must stay awake. Such threads must mark themselves unfreezable -like this: - - /* - * This thread doesn't need any user-level access, - * so get rid of all our resources. - */ - daemonize("usb-storage"); - - current->flags |= PF_NOFREEZE; - -from drivers/usb/storage/usb.c::usb_stor_control_thread() - -Such drivers are themselves responsible for staying quiet during -the actual snapshotting. |