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| author | Helge Deller <deller@gmx.de> | 2016-04-20 22:34:15 +0300 |
|---|---|---|
| committer | Helge Deller <deller@gmx.de> | 2016-05-22 22:39:25 +0300 |
| commit | 54b668009076caddbede8fde513ca2c982590bfe (patch) | |
| tree | 873f576cebe662cdb3c8a6626ba6be193a0a6ef4 /arch/parisc/include | |
| parent | 64e2a42bca12e408f0258c56adcf3595bcd116e7 (diff) | |
| download | linux-54b668009076caddbede8fde513ca2c982590bfe.tar.xz | |
parisc: Add native high-resolution sched_clock() implementation
Add a native implementation for the sched_clock() function which utilizes the
processor-internal cycle counter (Control Register 16) as high-resolution time
source.
With this patch we now get much more fine-grained resolutions in various
in-kernel time measurements (e.g. when viewing the function tracing logs), and
probably a more accurate scheduling on SMP systems.
There are a few specific implementation details in this patch:
1. On a 32bit kernel we emulate the higher 32bits of the required 64-bit
resolution of sched_clock() by increasing a per-cpu counter at every
wrap-around of the 32bit cycle counter.
2. In a SMP system, the cycle counters of the various CPUs are not syncronized
(similiar to the TSC in a x86_64 system). To cope with this we define
HAVE_UNSTABLE_SCHED_CLOCK and let the upper layers do the adjustment work.
3. Since we need HAVE_UNSTABLE_SCHED_CLOCK, we need to provide a cmpxchg64()
function even on a 32-bit kernel.
4. A 64-bit SMP kernel which is started on a UP system will mark the
sched_clock() implementation as "stable", which means that we don't expect any
jumps in the returned counter. This is true because we then run only on one
CPU.
Signed-off-by: Helge Deller <deller@gmx.de>
Diffstat (limited to 'arch/parisc/include')
| -rw-r--r-- | arch/parisc/include/asm/cmpxchg.h | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/arch/parisc/include/asm/cmpxchg.h b/arch/parisc/include/asm/cmpxchg.h index 0a90b965cccb..7ada30900807 100644 --- a/arch/parisc/include/asm/cmpxchg.h +++ b/arch/parisc/include/asm/cmpxchg.h @@ -52,8 +52,7 @@ extern void __cmpxchg_called_with_bad_pointer(void); /* __cmpxchg_u32/u64 defined in arch/parisc/lib/bitops.c */ extern unsigned long __cmpxchg_u32(volatile unsigned int *m, unsigned int old, unsigned int new_); -extern unsigned long __cmpxchg_u64(volatile unsigned long *ptr, - unsigned long old, unsigned long new_); +extern u64 __cmpxchg_u64(volatile u64 *ptr, u64 old, u64 new_); /* don't worry...optimizer will get rid of most of this */ static inline unsigned long @@ -61,7 +60,7 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new_, int size) { switch (size) { #ifdef CONFIG_64BIT - case 8: return __cmpxchg_u64((unsigned long *)ptr, old, new_); + case 8: return __cmpxchg_u64((u64 *)ptr, old, new_); #endif case 4: return __cmpxchg_u32((unsigned int *)ptr, (unsigned int)old, (unsigned int)new_); @@ -86,7 +85,7 @@ static inline unsigned long __cmpxchg_local(volatile void *ptr, { switch (size) { #ifdef CONFIG_64BIT - case 8: return __cmpxchg_u64((unsigned long *)ptr, old, new_); + case 8: return __cmpxchg_u64((u64 *)ptr, old, new_); #endif case 4: return __cmpxchg_u32(ptr, old, new_); default: @@ -111,4 +110,6 @@ static inline unsigned long __cmpxchg_local(volatile void *ptr, #define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n)) #endif +#define cmpxchg64(ptr, o, n) __cmpxchg_u64(ptr, o, n) + #endif /* _ASM_PARISC_CMPXCHG_H_ */ |