[S390] fix io_return critical section cleanup

If a machine check interrupts the io interrupt handler on one of the
instructions between io_return and io_leave the critical section
cleanup code will move the return psw to io_work_loop. By doing that
the switch from the asynchronous interrupt stack to the process stack
is skipped. If e.g. TIF_NEED_RESCHED is set things break because
the scheduler is called with the asynchronous interrupts stack.
Moving the psw back to io_return instead fixes the problem.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

2 files changed, 14 insertions, 2 deletions

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 4348f9bc5393..6af7045280a8 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -964,7 +964,7 @@ cleanup_critical:
         clc     4(4,%r12),BASED(cleanup_table_io_work_loop)
         bl      BASED(0f)
         clc     4(4,%r12),BASED(cleanup_table_io_work_loop+4)
-        bl      BASED(cleanup_io_return)
+        bl      BASED(cleanup_io_work_loop)
 0:
         br      %r14
 
@@ -1039,6 +1039,12 @@ cleanup_sysc_leave_insn:
 
 cleanup_io_return:
         mvc     __LC_RETURN_PSW(4),0(%r12)
+        mvc     __LC_RETURN_PSW+4(4),BASED(cleanup_table_io_return)
+        la      %r12,__LC_RETURN_PSW
+        br      %r14
+
+cleanup_io_work_loop:
+        mvc     __LC_RETURN_PSW(4),0(%r12)
         mvc     __LC_RETURN_PSW+4(4),BASED(cleanup_table_io_work_loop)
         la      %r12,__LC_RETURN_PSW
         br      %r14
diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S
index 29fd0f1e6ec4..52106d53271c 100644
--- a/arch/s390/kernel/entry64.S
+++ b/arch/s390/kernel/entry64.S
@@ -946,7 +946,7 @@ cleanup_critical:
         clc     8(8,%r12),BASED(cleanup_table_io_work_loop)
         jl      0f
         clc     8(8,%r12),BASED(cleanup_table_io_work_loop+8)
-        jl      cleanup_io_return
+        jl      cleanup_io_work_loop
 0:
         br      %r14
 
@@ -1021,6 +1021,12 @@ cleanup_sysc_leave_insn:
 
 cleanup_io_return:
         mvc     __LC_RETURN_PSW(8),0(%r12)
+        mvc     __LC_RETURN_PSW+8(8),BASED(cleanup_table_io_return)
+        la      %r12,__LC_RETURN_PSW
+        br      %r14
+
+cleanup_io_work_loop:
+        mvc     __LC_RETURN_PSW(8),0(%r12)
         mvc     __LC_RETURN_PSW+8(8),BASED(cleanup_table_io_work_loop)
         la      %r12,__LC_RETURN_PSW
         br      %r14