On Tue, Mar 13, 2018 at 1:31 PM, Chris Wilson chris@chris-wilson.co.uk wrote:
Quoting Arnd Bergmann (2018-03-13 12:08:29)
The conditional spinlock confuses gcc into thinking the 'flags' value might contain uninitialized data:
drivers/gpu/drm/i915/i915_pmu.c: In function '__i915_pmu_event_read': arch/x86/include/asm/paravirt_types.h:573:3: error: 'flags' may be used uninitialized in this function [-Werror=maybe-uninitialized]
The code is correct, but it's easy to see how the compiler gets confused here. This avoids the problem by pulling the lock outside of the function into its only caller.
Fixes: 1fe699e30113 ("drm/i915/pmu: Fix sleep under atomic in RC6 readout") Signed-off-by: Arnd Bergmann arnd@arndb.de
drivers/gpu/drm/i915/i915_pmu.c | 25 ++++++++++--------------- 1 file changed, 10 insertions(+), 15 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c index 4bc7aefa9541..2c8c705d1f18 100644 --- a/drivers/gpu/drm/i915/i915_pmu.c +++ b/drivers/gpu/drm/i915/i915_pmu.c @@ -415,7 +415,6 @@ static u64 __get_rc6(struct drm_i915_private *i915) static u64 get_rc6(struct drm_i915_private *i915, bool locked)
bool locked is now unused, right?
Right, removing it now.
val = get_rc6(i915, locked);break;
if (!locked) {unsigned long flags;spin_lock_irqsave(&i915->pmu.lock, flags);val = get_rc6(i915, locked);spin_unlock_irqrestore(&i915->pmu.lock, flags);break;} else {val = get_rc6(i915, locked);}break is now on one path only; should be here.
Fixed as well. I'll wait a bit for more comments before resending.
Thanks for the review!
Arnd