[S390] Fix kernel preemption.

When returning from IRQ handling and TIF_NEED_RESCHED is set we must
call preempt_schedule_irq() instead of schedule().
Otherwise the BKL might be unlocked in schedule() and therfore
everything that relies on the BKL is broken.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

2 files changed, 7 insertions, 20 deletions

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 764d56177cb..b2b2edc40eb 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -640,15 +640,9 @@ io_preempt:
 io_resume_loop:
         tm      __TI_flags+3(%r9),_TIF_NEED_RESCHED
         bno     BASED(io_restore)
-        mvc     __TI_precount(4,%r9),BASED(.Lc_pactive)
-        TRACE_IRQS_ON
-        stosm   __SF_EMPTY(%r15),0x03  # reenable interrupts
-        l       %r1,BASED(.Lschedule)
-        basr    %r14,%r1               # call schedule
-        stnsm   __SF_EMPTY(%r15),0xfc  # disable I/O and ext. interrupts
-        TRACE_IRQS_OFF
-        xc      __TI_precount(4,%r9),__TI_precount(%r9)
-        b       BASED(io_resume_loop)
+        l       %r1,BASED(.Lpreempt_schedule_irq)
+        la      %r14,BASED(io_resume_loop)
+        br      %r1                     # call schedule
 #endif
 
 #
@@ -1062,7 +1056,6 @@ cleanup_io_leave_insn:
                 .align  4
 .Lc_spsize:     .long   SP_SIZE
 .Lc_overhead:   .long   STACK_FRAME_OVERHEAD
-.Lc_pactive:    .long   PREEMPT_ACTIVE
 .Lnr_syscalls:  .long   NR_syscalls
 .L0x018:        .short  0x018
 .L0x020:        .short  0x020
@@ -1086,6 +1079,8 @@ cleanup_io_leave_insn:
 .Lexecve_tail:  .long   execve_tail
 .Ljump_table:   .long   pgm_check_table
 .Lschedule:     .long   schedule
+.Lpreempt_schedule_irq:
+                .long   preempt_schedule_irq
 .Ltrace:        .long   syscall_trace
 .Lschedtail:    .long   schedule_tail
 .Lsysc_table:   .long   sys_call_table
diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S
index e15c80efdd0..a3e47b893f0 100644
--- a/arch/s390/kernel/entry64.S
+++ b/arch/s390/kernel/entry64.S
@@ -623,15 +623,8 @@ io_preempt:
 io_resume_loop:
         tm      __TI_flags+7(%r9),_TIF_NEED_RESCHED
         jno     io_restore
-        larl    %r1,.Lc_pactive
-        mvc     __TI_precount(4,%r9),0(%r1)
-        TRACE_IRQS_ON
-        stosm   __SF_EMPTY(%r15),0x03   # reenable interrupts
-        brasl   %r14,schedule           # call schedule
-        stnsm   __SF_EMPTY(%r15),0xfc   # disable I/O and ext. interrupts
-        TRACE_IRQS_OFF
-        xc      __TI_precount(4,%r9),__TI_precount(%r9)
-        j       io_resume_loop
+        larl    %r14,io_resume_loop
+        jg      preempt_schedule_irq
 #endif
 
 #
@@ -1029,7 +1022,6 @@ cleanup_io_leave_insn:
  */
                 .align  4
 .Lconst:
-.Lc_pactive:    .long   PREEMPT_ACTIVE
 .Lnr_syscalls:  .long   NR_syscalls
 .L0x0130:       .short  0x130
 .L0x0140:       .short  0x140