From 3085982c6b45d7d22f76e3aa018affbc143a7370 Mon Sep 17 00:00:00 2001 From: Mika Kuoppala Date: Mon, 23 Apr 2018 14:37:53 +0300 Subject: [PATCH] drm/i915: Use ktime on wait_for MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit We use jiffies to determine when wait expires. However Imre did find out that jiffies can and will do a >1 increments on certain situations [1]. When this happens in a wait_for loop, we return timeout errorneously much earlier than what the real wallclock would say. We can't afford our waits to timeout prematurely. Discard jiffies and change to ktime to detect timeouts. v2: added bugzilla entry (Imre), added stable (Chris) Reported-by: Imre Deak References: https://lkml.org/lkml/2018/4/18/798 [1] Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105771 Cc: Imre Deak Cc: Chris Wilson Cc: Ville Syrjälä Cc: Signed-off-by: Mika Kuoppala Reviewed-by: Chris Wilson Link: https://patchwork.freedesktop.org/patch/msgid/20180423113754.28424-1-mika.kuoppala@linux.intel.com --- drivers/gpu/drm/i915/intel_drv.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h index 44ed248f1fe9..33ff2638c92b 100644 --- a/drivers/gpu/drm/i915/intel_drv.h +++ b/drivers/gpu/drm/i915/intel_drv.h @@ -49,12 +49,12 @@ * check the condition before the timeout. */ #define __wait_for(OP, COND, US, Wmin, Wmax) ({ \ - unsigned long timeout__ = jiffies + usecs_to_jiffies(US) + 1; \ + const ktime_t end__ = ktime_add_ns(ktime_get_raw(), 1000ll * (US)); \ long wait__ = (Wmin); /* recommended min for usleep is 10 us */ \ int ret__; \ might_sleep(); \ for (;;) { \ - bool expired__ = time_after(jiffies, timeout__); \ + const bool expired__ = ktime_after(ktime_get_raw(), end__); \ OP; \ if (COND) { \ ret__ = 0; \ -- GitLab