futex: Allow for compiling out PI support (bc2eecd7) · Commits · 戴 / test

include/linux/futex.h

+6 −1

Original line number	Diff line number	Diff line
		@@ -54,7 +54,6 @@ union futex_key {

		#ifdef CONFIG_FUTEX
		extern void exit_robust_list(struct task_struct *curr);
		extern void exit_pi_state_list(struct task_struct *curr);
		#ifdef CONFIG_HAVE_FUTEX_CMPXCHG
		#define futex_cmpxchg_enabled 1
		#else
		@@ -64,8 +63,14 @@ extern int futex_cmpxchg_enabled;
		static inline void exit_robust_list(struct task_struct *curr)
		{
		}
		#endif

		#ifdef CONFIG_FUTEX_PI
		extern void exit_pi_state_list(struct task_struct *curr);
		#else
		static inline void exit_pi_state_list(struct task_struct *curr)
		{
		}
		#endif

		#endif

init/Kconfig

+6 −1

Original line number	Diff line number	Diff line
		@@ -1275,12 +1275,17 @@ config BASE_FULL
		config FUTEX
		bool "Enable futex support" if EXPERT
		default y
		select RT_MUTEXES
		imply RT_MUTEXES
		help
		Disabling this option will cause the kernel to be built without
		support for "fast userspace mutexes". The resulting kernel may not
		run glibc-based applications correctly.

		config FUTEX_PI
		bool
		depends on FUTEX && RT_MUTEXES
		default y

		config HAVE_FUTEX_CMPXCHG
		bool
		depends on FUTEX

kernel/futex.c

+22 −0

Original line number	Diff line number	Diff line
		@@ -875,6 +875,8 @@ static struct task_struct *futex_find_get_task(pid_t pid)
		return p;
		}

		#ifdef CONFIG_FUTEX_PI

		/*
		* This task is holding PI mutexes at exit time => bad.
		* Kernel cleans up PI-state, but userspace is likely hosed.
		@@ -932,6 +934,8 @@ void exit_pi_state_list(struct task_struct *curr)
		raw_spin_unlock_irq(&curr->pi_lock);
		}

		#endif

		/*
		* We need to check the following states:
		*
		@@ -1799,6 +1803,15 @@ static int futex_requeue(u32 __user *uaddr1, unsigned int flags,
		struct futex_q this, next;
		DEFINE_WAKE_Q(wake_q);

		/*
		* When PI not supported: return -ENOSYS if requeue_pi is true,
		* consequently the compiler knows requeue_pi is always false past
		* this point which will optimize away all the conditional code
		* further down.
		*/
		if (!IS_ENABLED(CONFIG_FUTEX_PI) && requeue_pi)
		return -ENOSYS;

		if (requeue_pi) {
		/*
		* Requeue PI only works on two distinct uaddrs. This
		@@ -2594,6 +2607,9 @@ static int futex_lock_pi(u32 __user *uaddr, unsigned int flags,
		struct futex_q q = futex_q_init;
		int res, ret;

		if (!IS_ENABLED(CONFIG_FUTEX_PI))
		return -ENOSYS;

		if (refill_pi_state_cache())
		return -ENOMEM;

		@@ -2773,6 +2789,9 @@ static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags)
		struct futex_q *top_waiter;
		int ret;

		if (!IS_ENABLED(CONFIG_FUTEX_PI))
		return -ENOSYS;

		retry:
		if (get_user(uval, uaddr))
		return -EFAULT;
		@@ -2983,6 +3002,9 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
		struct futex_q q = futex_q_init;
		int res, ret;

		if (!IS_ENABLED(CONFIG_FUTEX_PI))
		return -ENOSYS;

		if (uaddr == uaddr2)
		return -EINVAL;

kernel/locking/rtmutex_common.h

+29 −0

Original line number	Diff line number	Diff line
		@@ -40,6 +40,9 @@ struct rt_mutex_waiter {
		/*
		* Various helpers to access the waiters-tree:
		*/

		#ifdef CONFIG_RT_MUTEXES

		static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
		{
		return !RB_EMPTY_ROOT(&lock->waiters);
		@@ -69,6 +72,32 @@ task_top_pi_waiter(struct task_struct *p)
		pi_tree_entry);
		}

		#else

		static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
		{
		return false;
		}

		static inline struct rt_mutex_waiter *
		rt_mutex_top_waiter(struct rt_mutex *lock)
		{
		return NULL;
		}

		static inline int task_has_pi_waiters(struct task_struct *p)
		{
		return false;
		}

		static inline struct rt_mutex_waiter *
		task_top_pi_waiter(struct task_struct *p)
		{
		return NULL;
		}

		#endif

		/*
		* lock->owner state tracking:
		*/

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