Commit fe06fe86 authored May 19, 2017 by Michael Ellerman

selftests/powerpc: Fix TM resched DSCR test with some compilers



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: 96d01610 ("powerpc: Correct DSCR during TM context switch")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Michael Neuling <mikey@neuling.org>

parent e41e53cd

tools/testing/selftests/powerpc/tm/tm-resched-dscr.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -42,12 +42,12 @@ int test_body(void)
		printf("Check DSCR TM context switch: ");
		fflush(stdout);
		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 */
		"tbegin.;"
		"beq 1f;"