diff options
Diffstat (limited to 'kernel/kmod.c')
| -rw-r--r-- | kernel/kmod.c | 89 |
1 files changed, 88 insertions, 1 deletions
diff --git a/kernel/kmod.c b/kernel/kmod.c index 78d365c524e..beedbdc6460 100644 --- a/kernel/kmod.c +++ b/kernel/kmod.c @@ -33,6 +33,8 @@ #include <linux/kernel.h> #include <linux/init.h> #include <linux/resource.h> +#include <linux/notifier.h> +#include <linux/suspend.h> #include <asm/uaccess.h> extern int max_threads; @@ -265,6 +267,88 @@ static void __call_usermodehelper(struct work_struct *work) } } +#ifdef CONFIG_PM +/* + * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY + * (used for preventing user land processes from being created after the user + * land has been frozen during a system-wide hibernation or suspend operation). + */ +static int usermodehelper_disabled; + +/* Number of helpers running */ +static atomic_t running_helpers = ATOMIC_INIT(0); + +/* + * Wait queue head used by usermodehelper_pm_callback() to wait for all running + * helpers to finish. + */ +static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq); + +/* + * Time to wait for running_helpers to become zero before the setting of + * usermodehelper_disabled in usermodehelper_pm_callback() fails + */ +#define RUNNING_HELPERS_TIMEOUT (5 * HZ) + +static int usermodehelper_pm_callback(struct notifier_block *nfb, + unsigned long action, + void *ignored) +{ + long retval; + + switch (action) { + case PM_HIBERNATION_PREPARE: + case PM_SUSPEND_PREPARE: + usermodehelper_disabled = 1; + smp_mb(); + /* + * From now on call_usermodehelper_exec() won't start any new + * helpers, so it is sufficient if running_helpers turns out to + * be zero at one point (it may be increased later, but that + * doesn't matter). + */ + retval = wait_event_timeout(running_helpers_waitq, + atomic_read(&running_helpers) == 0, + RUNNING_HELPERS_TIMEOUT); + if (retval) { + return NOTIFY_OK; + } else { + usermodehelper_disabled = 0; + return NOTIFY_BAD; + } + case PM_POST_HIBERNATION: + case PM_POST_SUSPEND: + usermodehelper_disabled = 0; + return NOTIFY_OK; + } + + return NOTIFY_DONE; +} + +static void helper_lock(void) +{ + atomic_inc(&running_helpers); + smp_mb__after_atomic_inc(); +} + +static void helper_unlock(void) +{ + if (atomic_dec_and_test(&running_helpers)) + wake_up(&running_helpers_waitq); +} + +static void register_pm_notifier_callback(void) +{ + pm_notifier(usermodehelper_pm_callback, 0); +} +#else /* CONFIG_PM */ +#define usermodehelper_disabled 0 + +static inline void helper_lock(void) {} +static inline void helper_unlock(void) {} +static inline void register_pm_notifier_callback(void) {} +#endif /* CONFIG_PM */ + /** * call_usermodehelper_setup - prepare to call a usermode helper * @path - path to usermode executable @@ -369,12 +453,13 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, DECLARE_COMPLETION_ONSTACK(done); int retval; + helper_lock(); if (sub_info->path[0] == '\0') { retval = 0; goto out; } - if (!khelper_wq) { + if (!khelper_wq || usermodehelper_disabled) { retval = -EBUSY; goto out; } @@ -390,6 +475,7 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, out: call_usermodehelper_freeinfo(sub_info); + helper_unlock(); return retval; } EXPORT_SYMBOL(call_usermodehelper_exec); @@ -431,4 +517,5 @@ void __init usermodehelper_init(void) { khelper_wq = create_singlethread_workqueue("khelper"); BUG_ON(!khelper_wq); + register_pm_notifier_callback(); } |