user/sven/linux.git/kernel/kmod.c, branch v3.4.44

PM / Sleep: Mitigate race between the freezer and request_firmware()

2012-03-28T21:30:28Z

There is a race condition between the freezer and request_firmware() such that if request_firmware() is run on one CPU and freeze_processes() is run on another CPU and usermodehelper_disable() called by it succeeds to grab umhelper_sem for writing before usermodehelper_read_trylock() called from request_firmware() acquires it for reading, the request_firmware() will fail and trigger a WARN_ON() complaining that it was called at a wrong time. However, in fact, it wasn't called at a wrong time and freeze_processes() simply happened to be executed simultaneously. To avoid this race, at least in some cases, modify usermodehelper_read_trylock() so that it doesn't fail if the freezing of tasks has just started and hasn't been completed yet. Instead, during the freezing of tasks, it will try to freeze the task that has called it so that it can wait until user space is thawed without triggering the scary warning. For this purpose, change usermodehelper_disabled so that it can take three different values, UMH_ENABLED (0), UMH_FREEZING and UMH_DISABLED. The first one means that usermode helpers are enabled, the last one means "hard disable" (i.e. the system is not ready for usermode helpers to be used) and the second one is reserved for the freezer. Namely, when freeze_processes() is started, it sets usermodehelper_disabled to UMH_FREEZING which tells usermodehelper_read_trylock() that it shouldn't fail just yet and should call try_to_freeze() if woken up and cannot return immediately. This way all freezable tasks that happen to call request_firmware() right before freeze_processes() is started and lose the race for umhelper_sem with it will be frozen and will sleep until thaw_processes() unsets usermodehelper_disabled. [For the non-freezable callers of request_firmware() the race for umhelper_sem against freeze_processes() is unfortunately unavoidable.] Reported-by: Stephen Boyd Signed-off-by: Rafael J. Wysocki Acked-by: Greg Kroah-Hartman Cc: stable@vger.kernel.org

firmware_class: Do not warn that system is not ready from async loads

2012-03-28T21:30:02Z

If firmware is requested asynchronously, by calling request_firmware_nowait(), there is no reason to fail the request (and warn the user) when the system is (presumably temporarily) unready to handle it (because user space is not available yet or frozen). For this reason, introduce an alternative routine for read-locking umhelper_sem, usermodehelper_read_lock_wait(), that will wait for usermodehelper_disabled to be unset (possibly with a timeout) and make request_firmware_work_func() use it instead of usermodehelper_read_trylock(). Accordingly, modify request_firmware() so that it uses usermodehelper_read_trylock() to acquire umhelper_sem and remove the code related to that lock from _request_firmware(). Signed-off-by: Rafael J. Wysocki Acked-by: Greg Kroah-Hartman Cc: stable@vger.kernel.org

firmware_class: Rework usermodehelper check

2012-03-28T21:29:45Z

Instead of two functions, read_lock_usermodehelper() and usermodehelper_is_disabled(), used in combination, introduce usermodehelper_read_trylock() that will only return with umhelper_sem held if usermodehelper_disabled is unset (and will return -EAGAIN otherwise) and make _request_firmware() use it. Rename read_unlock_usermodehelper() to usermodehelper_read_unlock() to follow the naming convention of the new function. Signed-off-by: Rafael J. Wysocki Acked-by: Greg Kroah-Hartman Cc: stable@vger.kernel.org

kmod: make __request_module() killable

2012-03-23T23:58:42Z

As Tetsuo Handa pointed out, request_module() can stress the system while the oom-killed caller sleeps in TASK_UNINTERRUPTIBLE. The task T uses "almost all" memory, then it does something which triggers request_module(). Say, it can simply call sys_socket(). This in turn needs more memory and leads to OOM. oom-killer correctly chooses T and kills it, but this can't help because it sleeps in TASK_UNINTERRUPTIBLE and after that oom-killer becomes "disabled" by the TIF_MEMDIE task T. Make __request_module() killable. The only necessary change is that call_modprobe() should kmalloc argv and module_name, they can't live in the stack if we use UMH_KILLABLE. This memory is freed via call_usermodehelper_freeinfo()->cleanup. Reported-by: Tetsuo Handa Signed-off-by: Oleg Nesterov Cc: Rusty Russell Cc: Tejun Heo Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kmod: introduce call_modprobe() helper

2012-03-23T23:58:42Z

No functional changes. Move the call_usermodehelper code from __request_module() into the new simple helper, call_modprobe(). Signed-off-by: Oleg Nesterov Cc: Tetsuo Handa Cc: Rusty Russell Cc: Tejun Heo Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

usermodehelper: ____call_usermodehelper() doesn't need do_exit()

2012-03-23T23:58:41Z

Minor cleanup. ____call_usermodehelper() can simply return, no need to call do_exit() explicitely. Signed-off-by: Oleg Nesterov Cc: Tetsuo Handa Cc: Rusty Russell Cc: Tejun Heo Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

usermodehelper: kill umh_wait, renumber UMH_* constants

2012-03-23T23:58:41Z

No functional changes. It is not sane to use UMH_KILLABLE with enum umh_wait, but obviously we do not want another argument in call_usermodehelper_* helpers. Kill this enum, use the plain int. Signed-off-by: Oleg Nesterov Cc: Tetsuo Handa Cc: Rusty Russell Cc: Tejun Heo Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

usermodehelper: implement UMH_KILLABLE

2012-03-23T23:58:41Z

Implement UMH_KILLABLE, should be used along with UMH_WAIT_EXEC/PROC. The caller must ensure that subprocess_info->path/etc can not go away until call_usermodehelper_freeinfo(). call_usermodehelper_exec(UMH_KILLABLE) does wait_for_completion_killable. If it fails, it uses xchg(&sub_info->complete, NULL) to serialize with umh_complete() which does the same xhcg() to access sub_info->complete. If call_usermodehelper_exec wins, it can safely return. umh_complete() should get NULL and call call_usermodehelper_freeinfo(). Otherwise we know that umh_complete() was already called, in this case call_usermodehelper_exec() falls back to wait_for_completion() which should succeed "very soon". Note: UMH_NO_WAIT == -1 but it obviously should not be used with UMH_KILLABLE. We delay the neccessary cleanup to simplify the back porting. Signed-off-by: Oleg Nesterov Cc: Tetsuo Handa Cc: Rusty Russell Cc: Tejun Heo Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

usermodehelper: introduce umh_complete(sub_info)

2012-03-23T23:58:41Z

Preparation. Add the new trivial helper, umh_complete(). Currently it simply does complete(sub_info->complete). Signed-off-by: Oleg Nesterov Cc: Tetsuo Handa Cc: Rusty Russell Cc: Tejun Heo Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge branch 'pm-sleep' into pm-for-linus

2011-12-25T22:42:20Z

* pm-sleep: (51 commits) PM: Drop generic_subsys_pm_ops PM / Sleep: Remove forward-only callbacks from AMBA bus type PM / Sleep: Remove forward-only callbacks from platform bus type PM: Run the driver callback directly if the subsystem one is not there PM / Sleep: Make pm_op() and pm_noirq_op() return callback pointers PM / Sleep: Merge internal functions in generic_ops.c PM / Sleep: Simplify generic system suspend callbacks PM / Hibernate: Remove deprecated hibernation snapshot ioctls PM / Sleep: Fix freezer failures due to racy usermodehelper_is_disabled() PM / Sleep: Recommend [un]lock_system_sleep() over using pm_mutex directly PM / Sleep: Replace mutex_[un]lock(&pm_mutex) with [un]lock_system_sleep() PM / Sleep: Make [un]lock_system_sleep() generic PM / Sleep: Use the freezer_count() functions in [un]lock_system_sleep() APIs PM / Freezer: Remove the "userspace only" constraint from freezer[_do_not]_count() PM / Hibernate: Replace unintuitive 'if' condition in kernel/power/user.c with 'else' Freezer / sunrpc / NFS: don't allow TASK_KILLABLE sleeps to block the freezer PM / Sleep: Unify diagnostic messages from device suspend/resume ACPI / PM: Do not save/restore NVS on Asus K54C/K54HR PM / Hibernate: Remove deprecated hibernation test modes PM / Hibernate: Thaw processes in SNAPSHOT_CREATE_IMAGE ioctl test path ... Conflicts: kernel/kmod.c