diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-hsi | 19 | ||||
| -rw-r--r-- | Documentation/power/freezing-of-tasks.txt | 37 | ||||
| -rw-r--r-- | Documentation/security/keys.txt | 14 |
3 files changed, 51 insertions, 19 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-hsi b/Documentation/ABI/testing/sysfs-bus-hsi new file mode 100644 index 00000000000..1b1b282a99e --- /dev/null +++ b/Documentation/ABI/testing/sysfs-bus-hsi @@ -0,0 +1,19 @@ +What: /sys/bus/hsi +Date: April 2012 +KernelVersion: 3.4 +Contact: Carlos Chinea <carlos.chinea@nokia.com> +Description: + High Speed Synchronous Serial Interface (HSI) is a + serial interface mainly used for connecting application + engines (APE) with cellular modem engines (CMT) in cellular + handsets. + The bus will be populated with devices (hsi_clients) representing + the protocols available in the system. Bus drivers implement + those protocols. + +What: /sys/bus/hsi/devices/.../modalias +Date: April 2012 +KernelVersion: 3.4 +Contact: Carlos Chinea <carlos.chinea@nokia.com> +Description: Stores the same MODALIAS value emitted by uevent + Format: hsi:<hsi_client device name> 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/Documentation/security/keys.txt b/Documentation/security/keys.txt index 78771709142..d389acd31e1 100644 --- a/Documentation/security/keys.txt +++ b/Documentation/security/keys.txt @@ -123,7 +123,7 @@ KEY SERVICE OVERVIEW The key service provides a number of features besides keys: - (*) The key service defines two special key types: + (*) The key service defines three special key types: (+) "keyring" @@ -137,6 +137,18 @@ The key service provides a number of features besides keys: blobs of data. These can be created, updated and read by userspace, and aren't intended for use by kernel services. + (+) "logon" + + Like a "user" key, a "logon" key has a payload that is an arbitrary + blob of data. It is intended as a place to store secrets which are + accessible to the kernel but not to userspace programs. + + The description can be arbitrary, but must be prefixed with a non-zero + length string that describes the key "subclass". The subclass is + separated from the rest of the description by a ':'. "logon" keys can + be created and updated from userspace, but the payload is only + readable from kernel space. + (*) Each process subscribes to three keyrings: a thread-specific keyring, a process-specific keyring, and a session-specific keyring. |