Peter Zijlstra | a787870 | 2013-08-14 14:55:40 +0200 | [diff] [blame^] | 1 | #ifndef __ASM_PREEMPT_H |
| 2 | #define __ASM_PREEMPT_H |
| 3 | |
| 4 | #include <linux/thread_info.h> |
| 5 | |
| 6 | /* |
| 7 | * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users |
| 8 | * that think a non-zero value indicates we cannot preempt. |
| 9 | */ |
| 10 | static __always_inline int preempt_count(void) |
| 11 | { |
| 12 | return current_thread_info()->preempt_count & ~PREEMPT_NEED_RESCHED; |
| 13 | } |
| 14 | |
| 15 | static __always_inline int *preempt_count_ptr(void) |
| 16 | { |
| 17 | return ¤t_thread_info()->preempt_count; |
| 18 | } |
| 19 | |
| 20 | /* |
| 21 | * We now loose PREEMPT_NEED_RESCHED and cause an extra reschedule; however the |
| 22 | * alternative is loosing a reschedule. Better schedule too often -- also this |
| 23 | * should be a very rare operation. |
| 24 | */ |
| 25 | static __always_inline void preempt_count_set(int pc) |
| 26 | { |
| 27 | *preempt_count_ptr() = pc; |
| 28 | } |
| 29 | |
| 30 | /* |
| 31 | * We fold the NEED_RESCHED bit into the preempt count such that |
| 32 | * preempt_enable() can decrement and test for needing to reschedule with a |
| 33 | * single instruction. |
| 34 | * |
| 35 | * We invert the actual bit, so that when the decrement hits 0 we know we both |
| 36 | * need to resched (the bit is cleared) and can resched (no preempt count). |
| 37 | */ |
| 38 | |
| 39 | static __always_inline void set_preempt_need_resched(void) |
| 40 | { |
| 41 | *preempt_count_ptr() &= ~PREEMPT_NEED_RESCHED; |
| 42 | } |
| 43 | |
| 44 | static __always_inline void clear_preempt_need_resched(void) |
| 45 | { |
| 46 | *preempt_count_ptr() |= PREEMPT_NEED_RESCHED; |
| 47 | } |
| 48 | |
| 49 | static __always_inline bool test_preempt_need_resched(void) |
| 50 | { |
| 51 | return !(*preempt_count_ptr() & PREEMPT_NEED_RESCHED); |
| 52 | } |
| 53 | |
| 54 | #endif /* __ASM_PREEMPT_H */ |