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authorHeiko Carstens <heiko.carstens@de.ibm.com>2010-10-25 16:10:18 +0200
committerMartin Schwidefsky <sky@mschwide.boeblingen.de.ibm.com>2010-10-25 16:10:16 +0200
commitfdb6d070effba1871f0bb980cf3c3b8738803414 (patch)
treea23343d98f472fb1fe8a2a4c8f86d269b64945bc /arch/s390/include
parentf861e4057263033ad9134bfd6745f91b2165b351 (diff)
downloadlinux-linaro-android-fdb6d070effba1871f0bb980cf3c3b8738803414.tar.gz
[S390] switch_to: dont restore/save access & fpu regs for kernel threads
If the previous task was a kernel thread there is no need to save the contents of the fpu and access registers since they aren't used in kernel mode. For the same reason it is not necessary to restore these registers if the next task is a kernel thread. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/include')
-rw-r--r--arch/s390/include/asm/system.h20
1 files changed, 12 insertions, 8 deletions
diff --git a/arch/s390/include/asm/system.h b/arch/s390/include/asm/system.h
index 1f2ebc4afd8..c35d0a383f0 100644
--- a/arch/s390/include/asm/system.h
+++ b/arch/s390/include/asm/system.h
@@ -85,14 +85,18 @@ static inline void restore_access_regs(unsigned int *acrs)
asm volatile("lam 0,15,%0" : : "Q" (*acrs));
}
-#define switch_to(prev,next,last) do { \
- if (prev == next) \
- break; \
- save_fp_regs(&prev->thread.fp_regs); \
- restore_fp_regs(&next->thread.fp_regs); \
- save_access_regs(&prev->thread.acrs[0]); \
- restore_access_regs(&next->thread.acrs[0]); \
- prev = __switch_to(prev,next); \
+#define switch_to(prev,next,last) do { \
+ if (prev == next) \
+ break; \
+ if (prev->mm) { \
+ save_fp_regs(&prev->thread.fp_regs); \
+ save_access_regs(&prev->thread.acrs[0]); \
+ } \
+ if (next->mm) { \
+ restore_fp_regs(&next->thread.fp_regs); \
+ restore_access_regs(&next->thread.acrs[0]); \
+ } \
+ prev = __switch_to(prev,next); \
} while (0)
extern void account_vtime(struct task_struct *, struct task_struct *);