On Tue, 11 Jul 2023, Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx> wrote: > Hi Lee, > > I'm really sorry for the late reply, I had some holidays in > between. > > On Tue, Jul 04, 2023 at 04:07:27PM +0800, Lee Shawn C wrote: >> Perform reboot stresss test on a kernel build with lockdebug flag enabled. >> Bad unlock balanace detected would happened sometimes. Below is the >> problematic scenario. If params.mmio_debug value was changed at step #4. >> And it would trigger this issue. Modify code flow that decide to >> enable/disable mmio debug before unclaimed_reg_debug() can avoid >> this symptom. >> >> 1. GEN6_READ_HEADER is called with params.mmio_debug = 0 >> 2. unclaimed_reg_debug(before = true) is called >> 3. unclaimed_reg_debug return without taking a lock >> because params.mmio_debug == 0 >> 4. other thread modifies params.mmio_debug to 1 >> 5. GEN6_READ_FOOTER is called with params.mmio_debug != 0 >> 6. unclaimed_reg_debug tries to assert non-taken lock (first WARN) >> 7. unclaimed_reg_debug tries to release non-taken lock (second WARN) >> >> Closes:https://gitlab.freedesktop.org/drm/intel/-/issues/8749 >> Signed-off-by: Lee Shawn C <shawn.c.lee@xxxxxxxxx> >> Cc: Uma Shankar <uma.shankar@xxxxxxxxx> >> Cc: Matt Roper <matthew.d.roper@xxxxxxxxx> >> Cc: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx> >> --- >> drivers/gpu/drm/i915/intel_uncore.c | 10 +++++----- >> 1 file changed, 5 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c >> index 796ebfe6c550..9d665978cc43 100644 >> --- a/drivers/gpu/drm/i915/intel_uncore.c >> +++ b/drivers/gpu/drm/i915/intel_uncore.c >> @@ -1931,9 +1931,6 @@ unclaimed_reg_debug(struct intel_uncore *uncore, >> const bool read, >> const bool before) >> { >> - if (likely(!uncore->i915->params.mmio_debug) || !uncore->debug) >> - return; >> - > > this is a very good catch! I'm fine with the change from my side: > > Reviewed-by: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx> Nope, there's a bug in the patch. https://lore.kernel.org/r/87ilb00zot.fsf@xxxxxxxxx > > But I'd like to hear from someone else, as well, Matt, Daniele? > > Thank you, > Andi -- Jani Nikula, Intel Open Source Graphics Center
