diff options
| -rw-r--r-- | arch/x86/include/asm/current.h | 2 | ||||
| -rw-r--r-- | arch/x86/include/asm/percpu.h | 26 | ||||
| -rw-r--r-- | arch/x86/include/asm/thread_info.h | 2 |
3 files changed, 21 insertions, 9 deletions
diff --git a/arch/x86/include/asm/current.h b/arch/x86/include/asm/current.h index c68c361..4d447b7 100644 --- a/arch/x86/include/asm/current.h +++ b/arch/x86/include/asm/current.h @@ -11,7 +11,7 @@ DECLARE_PER_CPU(struct task_struct *, current_task); static __always_inline struct task_struct *get_current(void) { - return percpu_read(current_task); + return percpu_read_stable(current_task); } #define current get_current() diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h index 103f1dd..04eacef 100644 --- a/arch/x86/include/asm/percpu.h +++ b/arch/x86/include/asm/percpu.h @@ -49,7 +49,7 @@ #define __percpu_arg(x) "%%"__stringify(__percpu_seg)":%P" #x #define __my_cpu_offset percpu_read(this_cpu_off) #else -#define __percpu_arg(x) "%" #x +#define __percpu_arg(x) "%P" #x #endif /* @@ -104,36 +104,48 @@ do { \ } \ } while (0) -#define percpu_from_op(op, var) \ +#define percpu_from_op(op, var, constraint) \ ({ \ typeof(var) ret__; \ switch (sizeof(var)) { \ case 1: \ asm(op "b "__percpu_arg(1)",%0" \ : "=q" (ret__) \ - : "m" (var)); \ + : constraint); \ break; \ case 2: \ asm(op "w "__percpu_arg(1)",%0" \ : "=r" (ret__) \ - : "m" (var)); \ + : constraint); \ break; \ case 4: \ asm(op "l "__percpu_arg(1)",%0" \ : "=r" (ret__) \ - : "m" (var)); \ + : constraint); \ break; \ case 8: \ asm(op "q "__percpu_arg(1)",%0" \ : "=r" (ret__) \ - : "m" (var)); \ + : constraint); \ break; \ default: __bad_percpu_size(); \ } \ ret__; \ }) -#define percpu_read(var) percpu_from_op("mov", per_cpu__##var) +/* + * percpu_read() makes gcc load the percpu variable every time it is + * accessed while percpu_read_stable() allows the value to be cached. + * percpu_read_stable() is more efficient and can be used if its value + * is guaranteed to be valid across cpus. The current users include + * get_current() and get_thread_info() both of which are actually + * per-thread variables implemented as per-cpu variables and thus + * stable for the duration of the respective task. + */ +#define percpu_read(var) percpu_from_op("mov", per_cpu__##var, \ + "m" (per_cpu__##var)) +#define percpu_read_stable(var) percpu_from_op("mov", per_cpu__##var, \ + "p" (&per_cpu__##var)) #define percpu_write(var, val) percpu_to_op("mov", per_cpu__##var, val) #define percpu_add(var, val) percpu_to_op("add", per_cpu__##var, val) #define percpu_sub(var, val) percpu_to_op("sub", per_cpu__##var, val) diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h index fad7d40..a1bb5a1 100644 --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -213,7 +213,7 @@ DECLARE_PER_CPU(unsigned long, kernel_stack); static inline struct thread_info *current_thread_info(void) { struct thread_info *ti; - ti = (void *)(percpu_read(kernel_stack) + + ti = (void *)(percpu_read_stable(kernel_stack) + KERNEL_STACK_OFFSET - THREAD_SIZE); return ti; } |