[ARM] Fix kernel mode preemption

Luc Van Oostenryck reported:

  The code removed by this patch tested the irq_cpustat_t members
  __local_irq_count and __local_bh_count but these fields have
  been removed some time ago:

  http://git.kernel.org/?p=linux/kernel/git/tglx/history.git;a=commitdiff;h=3ab146c93e039dec99fec8d441a8dd046fe510cc

Fix this oversight.

Acked-by:  Bill Gatliff <bgat@billgatliff.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 5 insertions, 19 deletions

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index a46d5b456765..65cef872c5f2 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -209,14 +209,12 @@ __irq_svc:
 
         irq_handler
 #ifdef CONFIG_PREEMPT
+        str     r8, [tsk, #TI_PREEMPT]          @ restore preempt count
         ldr     r0, [tsk, #TI_FLAGS]            @ get flags
+        teq     r8, #0                          @ if preempt count != 0
+        movne   r0, #0                          @ force flags to 0
         tst     r0, #_TIF_NEED_RESCHED
         blne    svc_preempt
-preempt_return:
-        ldr     r0, [tsk, #TI_PREEMPT]          @ read preempt value
-        str     r8, [tsk, #TI_PREEMPT]          @ restore preempt count
-        teq     r0, r7
-        strne   r0, [r0, -r0]                   @ bug()
 #endif
         ldr     r0, [sp, #S_PSR]                @ irqs are already disabled
         msr     spsr_cxsf, r0
@@ -230,19 +228,11 @@ preempt_return:
 
 #ifdef CONFIG_PREEMPT
 svc_preempt:
-        teq     r8, #0                          @ was preempt count = 0
-        ldreq   r6, .LCirq_stat
-        movne   pc, lr                          @ no
-        ldr     r0, [r6, #4]                    @ local_irq_count
-        ldr     r1, [r6, #8]                    @ local_bh_count
-        adds    r0, r0, r1
-        movne   pc, lr
-        mov     r7, #0                          @ preempt_schedule_irq
-        str     r7, [tsk, #TI_PREEMPT]          @ expects preempt_count == 0
+        mov     r8, lr
 1:      bl      preempt_schedule_irq            @ irq en/disable is done inside
         ldr     r0, [tsk, #TI_FLAGS]            @ get new tasks TI_FLAGS
         tst     r0, #_TIF_NEED_RESCHED
-        beq     preempt_return                  @ go again
+        moveq   pc, r8                          @ go again
         b       1b
 #endif
 
@@ -326,10 +316,6 @@ __pabt_svc:
 #endif
 .LCfp:
         .word   fp_enter
-#ifdef CONFIG_PREEMPT
-.LCirq_stat:
-        .word   irq_stat
-#endif
 
 /*
  * User mode handlers