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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
CC:     Michael Ellerman <mpe@ellerman.id.au>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.4 054/167] selftests/powerpc: Fix TM resched
 DSCR test with some compilers
Thread-Topic: [PATCH AUTOSEL for 4.4 054/167] selftests/powerpc: Fix TM
 resched DSCR test with some compilers
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Date:   Mon, 19 Mar 2018 16:06:28 +0000
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From: Michael Ellerman <mpe@ellerman.id.au>

[ 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 "=3Dr"), 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 <mpe@ellerman.id.au>
Acked-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 tools/testing/selftests/powerpc/tm/tm-resched-dscr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/powerpc/tm/tm-resched-dscr.c b/tools/t=
esting/selftests/powerpc/tm/tm-resched-dscr.c
index 42d4c8caad81..de8dc82e2567 100644
--- 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: ");
 	fflush(stdout);
 	for (;;) {
-		rv =3D 1;
 		asm __volatile__ (
 			/* set a known value into the DSCR */
 			"ld      3, %[dscr1];"
 			"mtspr   %[sprn_dscr], 3;"
=20
+			"li      %[rv], 1;"
 			/* start and suspend a transaction */
 			TBEGIN
 			"beq     1f;"
--=20
2.14.1