diff options
| -rw-r--r-- | Documentation/power/freezing-of-tasks.txt | 37 | ||||
| -rw-r--r-- | kernel/power/swap.c | 28 |
2 files changed, 41 insertions, 24 deletions
diff --git a/Documentation/power/freezing-of-tasks.txt b/Documentation/power/freezing-of-tasks.txt index ec715cd78fb..6ec291ea1c7 100644 --- a/Documentation/power/freezing-of-tasks.txt +++ b/Documentation/power/freezing-of-tasks.txt @@ -9,7 +9,7 @@ architectures). II. How does it work? -There are four per-task flags used for that, PF_NOFREEZE, PF_FROZEN, TIF_FREEZE +There are three per-task flags used for that, PF_NOFREEZE, PF_FROZEN and PF_FREEZER_SKIP (the last one is auxiliary). The tasks that have PF_NOFREEZE unset (all user space processes and some kernel threads) are regarded as 'freezable' and treated in a special way before the system enters a @@ -17,30 +17,31 @@ suspend state as well as before a hibernation image is created (in what follows we only consider hibernation, but the description also applies to suspend). Namely, as the first step of the hibernation procedure the function -freeze_processes() (defined in kernel/power/process.c) is called. It executes -try_to_freeze_tasks() that sets TIF_FREEZE for all of the freezable tasks and -either wakes them up, if they are kernel threads, or sends fake signals to them, -if they are user space processes. A task that has TIF_FREEZE set, should react -to it by calling the function called __refrigerator() (defined in -kernel/freezer.c), which sets the task's PF_FROZEN flag, changes its state -to TASK_UNINTERRUPTIBLE and makes it loop until PF_FROZEN is cleared for it. -Then, we say that the task is 'frozen' and therefore the set of functions -handling this mechanism is referred to as 'the freezer' (these functions are -defined in kernel/power/process.c, kernel/freezer.c & include/linux/freezer.h). -User space processes are generally frozen before kernel threads. +freeze_processes() (defined in kernel/power/process.c) is called. A system-wide +variable system_freezing_cnt (as opposed to a per-task flag) is used to indicate +whether the system is to undergo a freezing operation. And freeze_processes() +sets this variable. After this, it executes try_to_freeze_tasks() that sends a +fake signal to all user space processes, and wakes up all the kernel threads. +All freezable tasks must react to that by calling try_to_freeze(), which +results in a call to __refrigerator() (defined in kernel/freezer.c), which sets +the task's PF_FROZEN flag, changes its state to TASK_UNINTERRUPTIBLE and makes +it loop until PF_FROZEN is cleared for it. Then, we say that the task is +'frozen' and therefore the set of functions handling this mechanism is referred +to as 'the freezer' (these functions are defined in kernel/power/process.c, +kernel/freezer.c & include/linux/freezer.h). User space processes are generally +frozen before kernel threads. __refrigerator() must not be called directly. Instead, use the try_to_freeze() function (defined in include/linux/freezer.h), that checks -the task's TIF_FREEZE flag and makes the task enter __refrigerator() if the -flag is set. +if the task is to be frozen and makes the task enter __refrigerator(). For user space processes try_to_freeze() is called automatically from the signal-handling code, but the freezable kernel threads need to call it explicitly in suitable places or use the wait_event_freezable() or wait_event_freezable_timeout() macros (defined in include/linux/freezer.h) -that combine interruptible sleep with checking if TIF_FREEZE is set and calling -try_to_freeze(). The main loop of a freezable kernel thread may look like the -following one: +that combine interruptible sleep with checking if the task is to be frozen and +calling try_to_freeze(). The main loop of a freezable kernel thread may look +like the following one: set_freezable(); do { @@ -53,7 +54,7 @@ following one: (from drivers/usb/core/hub.c::hub_thread()). If a freezable kernel thread fails to call try_to_freeze() after the freezer has -set TIF_FREEZE for it, the freezing of tasks will fail and the entire +initiated a freezing operation, the freezing of tasks will fail and the entire hibernation operation will be cancelled. For this reason, freezable kernel threads must call try_to_freeze() somewhere or use one of the wait_event_freezable() and wait_event_freezable_timeout() macros. diff --git a/kernel/power/swap.c b/kernel/power/swap.c index 8742fd013a9..eef311a58a6 100644 --- a/kernel/power/swap.c +++ b/kernel/power/swap.c @@ -51,6 +51,23 @@ #define MAP_PAGE_ENTRIES (PAGE_SIZE / sizeof(sector_t) - 1) +/* + * Number of free pages that are not high. + */ +static inline unsigned long low_free_pages(void) +{ + return nr_free_pages() - nr_free_highpages(); +} + +/* + * Number of pages required to be kept free while writing the image. Always + * half of all available low pages before the writing starts. + */ +static inline unsigned long reqd_free_pages(void) +{ + return low_free_pages() / 2; +} + struct swap_map_page { sector_t entries[MAP_PAGE_ENTRIES]; sector_t next_swap; @@ -72,7 +89,7 @@ struct swap_map_handle { sector_t cur_swap; sector_t first_sector; unsigned int k; - unsigned long nr_free_pages, written; + unsigned long reqd_free_pages; u32 crc32; }; @@ -316,8 +333,7 @@ static int get_swap_writer(struct swap_map_handle *handle) goto err_rel; } handle->k = 0; - handle->nr_free_pages = nr_free_pages() >> 1; - handle->written = 0; + handle->reqd_free_pages = reqd_free_pages(); handle->first_sector = handle->cur_swap; return 0; err_rel: @@ -352,11 +368,11 @@ static int swap_write_page(struct swap_map_handle *handle, void *buf, handle->cur_swap = offset; handle->k = 0; } - if (bio_chain && ++handle->written > handle->nr_free_pages) { + if (bio_chain && low_free_pages() <= handle->reqd_free_pages) { error = hib_wait_on_bio_chain(bio_chain); if (error) goto out; - handle->written = 0; + handle->reqd_free_pages = reqd_free_pages(); } out: return error; @@ -618,7 +634,7 @@ static int save_image_lzo(struct swap_map_handle *handle, * Adjust number of free pages after all allocations have been done. * We don't want to run out of pages when writing. */ - handle->nr_free_pages = nr_free_pages() >> 1; + handle->reqd_free_pages = reqd_free_pages(); /* * Start the CRC32 thread. |