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Subject[PATCH 4.4 053/190] selftests/powerpc: Fix TM resched DSCR test with some compilers
4.4-stable review patch.  If anyone has any objections, please let me know.


From: Michael Ellerman <>

[ Upstream commit fe06fe860250a4f01d0eaf70a2563b1997174a74 ]

The tm-resched-dscr test has started failing sometimes, depending on
what compiler it's built with, eg:

test: tm_resched_dscr
Check DSCR TM context switch: tm-resched-dscr: tm-resched-dscr.c:76: test_body: Assertion `rv' failed.
!! child died by signal 6

When it fails we see that the compiler doesn't initialise rv to 1 before
entering the inline asm block. Although that's counter intuitive, it
is allowed because we tell the compiler that the inline asm will write
to rv (using "=r"), meaning the original value is irrelevant.

Marking it as a read/write parameter would presumably work, but it seems
simpler to fix it by setting the initial value of rv in the inline asm.

Fixes: 96d016108640 ("powerpc: Correct DSCR during TM context switch")
Signed-off-by: Michael Ellerman <>
Acked-by: Michael Neuling <>
Signed-off-by: Sasha Levin <>
Signed-off-by: Greg Kroah-Hartman <>
tools/testing/selftests/powerpc/tm/tm-resched-dscr.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/tools/testing/selftests/powerpc/tm/tm-resched-dscr.c
+++ b/tools/testing/selftests/powerpc/tm/tm-resched-dscr.c
@@ -45,12 +45,12 @@ int test_body(void)
printf("Check DSCR TM context switch: ");
for (;;) {
- rv = 1;
asm __volatile__ (
/* set a known value into the DSCR */
"ld 3, %[dscr1];"
"mtspr %[sprn_dscr], 3;"

+ "li %[rv], 1;"
/* start and suspend a transaction */
"beq 1f;"

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