s390: initialize backchain for ext_int_handler()

To allow correct stack backtraces the backchain for the external
interrupt handler is now initialized with zero like it is already
done for example by io_int_handler().

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S
index 4e1c292fa7e3b21068c238f2b334b53e7b67ce21..6b5ea904e99703d59db7afcec8e2c9e4391f34e3 100644 (file)
--- a/arch/s390/kernel/entry64.S
+++ b/arch/s390/kernel/entry64.S
@@ -622,6 +622,7 @@ ext_skip:
        mvc     __PT_R8(64,%r11),__LC_SAVE_AREA_ASYNC
        stmg    %r8,%r9,__PT_PSW(%r11)
        TRACE_IRQS_OFF
+       xc      __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
        lghi    %r1,4096
        lgr     %r2,%r11                # pass pointer to pt_regs
        llgf    %r3,__LC_EXT_CPU_ADDR   # get cpu address + interruption code