diff options
Diffstat (limited to 'Documentation/power')
| -rw-r--r-- | Documentation/power/kernel_threads.txt | 40 | ||||
| -rw-r--r-- | Documentation/power/pci.txt | 37 | ||||
| -rw-r--r-- | Documentation/power/swsusp.txt | 21 |
3 files changed, 7 insertions, 91 deletions
diff --git a/Documentation/power/kernel_threads.txt b/Documentation/power/kernel_threads.txt deleted file mode 100644 index fb57784986b1..000000000000 --- 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. diff --git a/Documentation/power/pci.txt b/Documentation/power/pci.txt index e00b099a4b86..dd8fe43888d3 100644 --- a/Documentation/power/pci.txt +++ b/Documentation/power/pci.txt @@ -164,7 +164,6 @@ struct pci_driver: int (*suspend) (struct pci_dev *dev, pm_message_t state); int (*resume) (struct pci_dev *dev); - int (*enable_wake) (struct pci_dev *dev, pci_power_t state, int enable); suspend @@ -251,42 +250,6 @@ The driver should update the current_state field in its pci_dev structure in this function, except for PM-capable devices when pci_set_power_state is used. -enable_wake ------------ - -Usage: - -if (dev->driver && dev->driver->enable_wake) - dev->driver->enable_wake(dev,state,enable); - -This callback is generally only relevant for devices that support the PCI PM -spec and have the ability to generate a PME# (Power Management Event Signal) -to wake the system up. (However, it is possible that a device may support -some non-standard way of generating a wake event on sleep.) - -Bits 15:11 of the PMC (Power Mgmt Capabilities) Register in a device's -PM Capabilities describe what power states the device supports generating a -wake event from: - -+------------------+ -| Bit | State | -+------------------+ -| 11 | D0 | -| 12 | D1 | -| 13 | D2 | -| 14 | D3hot | -| 15 | D3cold | -+------------------+ - -A device can use this to enable wake events: - - pci_enable_wake(dev,state,enable); - -Note that to enable PME# from D3cold, a value of 4 should be passed to -pci_enable_wake (since it uses an index into a bitmask). If a driver gets -a request to enable wake events from D3, two calls should be made to -pci_enable_wake (one for both D3hot and D3cold). - A reference implementation ------------------------- diff --git a/Documentation/power/swsusp.txt b/Documentation/power/swsusp.txt index 5b8d6953f05e..aea7e9209667 100644 --- a/Documentation/power/swsusp.txt +++ b/Documentation/power/swsusp.txt @@ -140,21 +140,11 @@ should be sent to the mailing list available through the suspend2 website, and not to the Linux Kernel Mailing List. We are working toward merging suspend2 into the mainline kernel. -Q: A kernel thread must voluntarily freeze itself (call 'refrigerator'). -I found some kernel threads that don't do it, and they don't freeze -so the system can't sleep. Is this a known behavior? - -A: All such kernel threads need to be fixed, one by one. Select the -place where the thread is safe to be frozen (no kernel semaphores -should be held at that point and it must be safe to sleep there), and -add: - - try_to_freeze(); - -If the thread is needed for writing the image to storage, you should -instead set the PF_NOFREEZE process flag when creating the thread (and -be very careful). +Q: What is the freezing of tasks and why are we using it? +A: The freezing of tasks is a mechanism by which user space processes and some +kernel threads are controlled during hibernation or system-wide suspend (on some +architectures). See freezing-of-tasks.txt for details. Q: What is the difference between "platform" and "shutdown"? @@ -393,6 +383,9 @@ safest thing is to unmount all filesystems on removable media (such USB, Firewire, CompactFlash, MMC, external SATA, or even IDE hotplug bays) before suspending; then remount them after resuming. +There is a work-around for this problem. For more information, see +Documentation/usb/persist.txt. + Q: I upgraded the kernel from 2.6.15 to 2.6.16. Both kernels were compiled with the similar configuration files. Anyway I found that suspend to disk (and resume) is much slower on 2.6.16 compared to |