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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2008-05-07 09:22:52 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2008-05-07 09:23:00 +0200
commit2688905e6a9b3647bf7b452cb0ff2bdb166bd8fe (patch)
tree389b9c29eaaa7eb49a9e7d3bb601959fb9d27af8 /arch/s390/kernel/entry.S
parentc0a18111e571138747a98af18b3a2124df56a0d1 (diff)
downloadop-kernel-dev-2688905e6a9b3647bf7b452cb0ff2bdb166bd8fe.zip
op-kernel-dev-2688905e6a9b3647bf7b452cb0ff2bdb166bd8fe.tar.gz
[S390] s390: Optimize user and work TIF check
On return from syscall or interrupt, we have to check if we return to userspace (likely) and if there is work todo (less likely) to decide if we handle the work. We can optimize this check: we first check for the less likely work case and then check for userspace. This patch is also a preparation for an additional patch, that fixes a bug in KVM dealing with cpu bound guests. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel/entry.S')
-rw-r--r--arch/s390/kernel/entry.S29
1 files changed, 14 insertions, 15 deletions
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index bdbb3bc..708cf9c 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -279,8 +279,6 @@ sysc_do_restart:
st %r2,SP_R2(%r15) # store return value (change R2 on stack)
sysc_return:
- tm SP_PSW+1(%r15),0x01 # returning to user ?
- bno BASED(sysc_restore)
tm __TI_flags+3(%r9),_TIF_WORK_SVC
bnz BASED(sysc_work) # there is work to do (signals etc.)
sysc_restore:
@@ -312,6 +310,8 @@ sysc_work_loop:
# One of the work bits is on. Find out which one.
#
sysc_work:
+ tm SP_PSW+1(%r15),0x01 # returning to user ?
+ bno BASED(sysc_restore)
tm __TI_flags+3(%r9),_TIF_MCCK_PENDING
bo BASED(sysc_mcck_pending)
tm __TI_flags+3(%r9),_TIF_NEED_RESCHED
@@ -602,12 +602,6 @@ io_no_vtime:
la %r2,SP_PTREGS(%r15) # address of register-save area
basr %r14,%r1 # branch to standard irq handler
io_return:
- tm SP_PSW+1(%r15),0x01 # returning to user ?
-#ifdef CONFIG_PREEMPT
- bno BASED(io_preempt) # no -> check for preemptive scheduling
-#else
- bno BASED(io_restore) # no-> skip resched & signal
-#endif
tm __TI_flags+3(%r9),_TIF_WORK_INT
bnz BASED(io_work) # there is work to do (signals etc.)
io_restore:
@@ -629,10 +623,18 @@ io_restore_trace_psw:
.long 0, io_restore_trace + 0x80000000
#endif
-#ifdef CONFIG_PREEMPT
-io_preempt:
+#
+# switch to kernel stack, then check the TIF bits
+#
+io_work:
+ tm SP_PSW+1(%r15),0x01 # returning to user ?
+#ifndef CONFIG_PREEMPT
+ bno BASED(io_restore) # no-> skip resched & signal
+#else
+ bnz BASED(io_work_user) # no -> check for preemptive scheduling
+ # check for preemptive scheduling
icm %r0,15,__TI_precount(%r9)
- bnz BASED(io_restore)
+ bnz BASED(io_restore) # preemption disabled
l %r1,SP_R15(%r15)
s %r1,BASED(.Lc_spsize)
mvc SP_PTREGS(__PT_SIZE,%r1),SP_PTREGS(%r15)
@@ -646,10 +648,7 @@ io_resume_loop:
br %r1 # call schedule
#endif
-#
-# switch to kernel stack, then check the TIF bits
-#
-io_work:
+io_work_user:
l %r1,__LC_KERNEL_STACK
s %r1,BASED(.Lc_spsize)
mvc SP_PTREGS(__PT_SIZE,%r1),SP_PTREGS(%r15)
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