Commit bc2eecd7 authored by Nicolas Pitre's avatar Nicolas Pitre Committed by Thomas Gleixner

futex: Allow for compiling out PI support

This makes it possible to preserve basic futex support and compile out the
PI support when RT mutexes are not available.
Signed-off-by: 's avatarNicolas Pitre <nico@linaro.org>
Signed-off-by: 's avatarThomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <dvhart@infradead.org>
Link: http://lkml.kernel.org/r/alpine.LFD.2.20.1708010024190.5981@knanqh.ubzr
parent f06e8c58
......@@ -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
......@@ -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
......
......@@ -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;
......
......@@ -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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