diff options
Diffstat (limited to 'lib/kernel_lock.c')
| -rw-r--r-- | lib/kernel_lock.c | 123 |
1 files changed, 0 insertions, 123 deletions
diff --git a/lib/kernel_lock.c b/lib/kernel_lock.c index f73e2f8c308f..812dbf00844b 100644 --- a/lib/kernel_lock.c +++ b/lib/kernel_lock.c | |||
| @@ -9,7 +9,6 @@ | |||
| 9 | #include <linux/module.h> | 9 | #include <linux/module.h> |
| 10 | #include <linux/kallsyms.h> | 10 | #include <linux/kallsyms.h> |
| 11 | 11 | ||
| 12 | #ifdef CONFIG_PREEMPT_BKL | ||
| 13 | /* | 12 | /* |
| 14 | * The 'big kernel semaphore' | 13 | * The 'big kernel semaphore' |
| 15 | * | 14 | * |
| @@ -86,128 +85,6 @@ void __lockfunc unlock_kernel(void) | |||
| 86 | up(&kernel_sem); | 85 | up(&kernel_sem); |
| 87 | } | 86 | } |
| 88 | 87 | ||
| 89 | #else | ||
| 90 | |||
| 91 | /* | ||
| 92 | * The 'big kernel lock' | ||
| 93 | * | ||
| 94 | * This spinlock is taken and released recursively by lock_kernel() | ||
| 95 | * and unlock_kernel(). It is transparently dropped and reacquired | ||
| 96 | * over schedule(). It is used to protect legacy code that hasn't | ||
| 97 | * been migrated to a proper locking design yet. | ||
| 98 | * | ||
| 99 | * Don't use in new code. | ||
| 100 | */ | ||
| 101 | static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kernel_flag); | ||
| 102 | |||
| 103 | |||
| 104 | /* | ||
| 105 | * Acquire/release the underlying lock from the scheduler. | ||
| 106 | * | ||
| 107 | * This is called with preemption disabled, and should | ||
| 108 | * return an error value if it cannot get the lock and | ||
| 109 | * TIF_NEED_RESCHED gets set. | ||
| 110 | * | ||
| 111 | * If it successfully gets the lock, it should increment | ||
| 112 | * the preemption count like any spinlock does. | ||
| 113 | * | ||
| 114 | * (This works on UP too - _raw_spin_trylock will never | ||
| 115 | * return false in that case) | ||
| 116 | */ | ||
| 117 | int __lockfunc __reacquire_kernel_lock(void) | ||
| 118 | { | ||
| 119 | while (!_raw_spin_trylock(&kernel_flag)) { | ||
| 120 | if (test_thread_flag(TIF_NEED_RESCHED)) | ||
| 121 | return -EAGAIN; | ||
| 122 | cpu_relax(); | ||
| 123 | } | ||
| 124 | preempt_disable(); | ||
| 125 | return 0; | ||
| 126 | } | ||
| 127 | |||
| 128 | void __lockfunc __release_kernel_lock(void) | ||
| 129 | { | ||
| 130 | _raw_spin_unlock(&kernel_flag); | ||
| 131 | preempt_enable_no_resched(); | ||
| 132 | } | ||
| 133 | |||
| 134 | /* | ||
| 135 | * These are the BKL spinlocks - we try to be polite about preemption. | ||
| 136 | * If SMP is not on (ie UP preemption), this all goes away because the | ||
| 137 | * _raw_spin_trylock() will always succeed. | ||
| 138 | */ | ||
| 139 | #ifdef CONFIG_PREEMPT | ||
| 140 | static inline void __lock_kernel(void) | ||
| 141 | { | ||
| 142 | preempt_disable(); | ||
| 143 | if (unlikely(!_raw_spin_trylock(&kernel_flag))) { | ||
| 144 | /* | ||
| 145 | * If preemption was disabled even before this | ||
| 146 | * was called, there's nothing we can be polite | ||
| 147 | * about - just spin. | ||
| 148 | */ | ||
| 149 | if (preempt_count() > 1) { | ||
| 150 | _raw_spin_lock(&kernel_flag); | ||
| 151 | return; | ||
| 152 | } | ||
| 153 | |||
| 154 | /* | ||
| 155 | * Otherwise, let's wait for the kernel lock | ||
| 156 | * with preemption enabled.. | ||
| 157 | */ | ||
| 158 | do { | ||
| 159 | preempt_enable(); | ||
| 160 | while (spin_is_locked(&kernel_flag)) | ||
| 161 | cpu_relax(); | ||
| 162 | preempt_disable(); | ||
| 163 | } while (!_raw_spin_trylock(&kernel_flag)); | ||
| 164 | } | ||
| 165 | } | ||
| 166 | |||
| 167 | #else | ||
| 168 | |||
| 169 | /* | ||
| 170 | * Non-preemption case - just get the spinlock | ||
| 171 | */ | ||
| 172 | static inline void __lock_kernel(void) | ||
| 173 | { | ||
| 174 | _raw_spin_lock(&kernel_flag); | ||
| 175 | } | ||
| 176 | #endif | ||
| 177 | |||
| 178 | static inline void __unlock_kernel(void) | ||
| 179 | { | ||
| 180 | /* | ||
| 181 | * the BKL is not covered by lockdep, so we open-code the | ||
| 182 | * unlocking sequence (and thus avoid the dep-chain ops): | ||
| 183 | */ | ||
| 184 | _raw_spin_unlock(&kernel_flag); | ||
| 185 | preempt_enable(); | ||
| 186 | } | ||
| 187 | |||
| 188 | /* | ||
| 189 | * Getting the big kernel lock. | ||
| 190 | * | ||
| 191 | * This cannot happen asynchronously, so we only need to | ||
| 192 | * worry about other CPU's. | ||
| 193 | */ | ||
| 194 | void __lockfunc lock_kernel(void) | ||
| 195 | { | ||
| 196 | int depth = current->lock_depth+1; | ||
| 197 | if (likely(!depth)) | ||
| 198 | __lock_kernel(); | ||
| 199 | current->lock_depth = depth; | ||
| 200 | } | ||
| 201 | |||
| 202 | void __lockfunc unlock_kernel(void) | ||
| 203 | { | ||
| 204 | BUG_ON(current->lock_depth < 0); | ||
| 205 | if (likely(--current->lock_depth < 0)) | ||
| 206 | __unlock_kernel(); | ||
| 207 | } | ||
| 208 | |||
| 209 | #endif | ||
| 210 | |||
| 211 | EXPORT_SYMBOL(lock_kernel); | 88 | EXPORT_SYMBOL(lock_kernel); |
| 212 | EXPORT_SYMBOL(unlock_kernel); | 89 | EXPORT_SYMBOL(unlock_kernel); |
| 213 | 90 | ||
