selftests/powerpc: Fix TM resched DSCR test with some compilers
authorMichael Ellerman <mpe@ellerman.id.au>
Fri, 19 May 2017 01:29:04 +0000 (11:29 +1000)
committerMichael Ellerman <mpe@ellerman.id.au>
Fri, 19 May 2017 09:46:34 +0000 (19:46 +1000)
commitfe06fe860250a4f01d0eaf70a2563b1997174a74
tree0bcce900e1a98434d35aa9bf6e9a4dfccc80d800
parente41e53cd4fe331d0d1f06f8e4ed7e2cc63ee2c34
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: 96d016108640 ("powerpc: Correct DSCR during TM context switch")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Michael Neuling <mikey@neuling.org>
tools/testing/selftests/powerpc/tm/tm-resched-dscr.c