On 28/11/14 09:29, Daniel Vetter wrote: > We've lost the +1 required for correct timeouts in > > commit 5ed0bdf21a85d78e04f89f15ccf227562177cbd9 > Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Date: Wed Jul 16 21:05:06 2014 +0000 > > drm: i915: Use nsec based interfaces > > Use ktime_get_raw_ns() and get rid of the back and forth timespec > conversions. > > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx> > Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx> > > So fix this up by reinstating our handrolled _timeout function. While > at it bother with handling MAX_JIFFIES. > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=82749 > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: John Stultz <john.stultz@xxxxxxxxxx> > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> > --- > drivers/gpu/drm/i915/i915_drv.h | 10 ++++++++++ > drivers/gpu/drm/i915/i915_gem.c | 3 ++- > 2 files changed, 12 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h > index 02b3cb32c8a6..caae337c0199 100644 > --- a/drivers/gpu/drm/i915/i915_drv.h > +++ b/drivers/gpu/drm/i915/i915_drv.h > @@ -3030,6 +3030,16 @@ static inline unsigned long msecs_to_jiffies_timeout(const unsigned int m) > return min_t(unsigned long, MAX_JIFFY_OFFSET, j + 1); > } > > +static inline unsigned long nsecs_to_jiffies_timeout(const u64 m) > +{ > + unsigned long j = nsecs_to_jiffies(m); nsecs_to_jiffies() may be (relatively) expensive (mul/div/etc), so I'd be inclined to move the call until after the test below. It would be nice if the test turned into a single comparison, since the RHS is a constant for a given kernel build; but it looks like jiffies_to_usecs() isn't expanded inline, since it's in time.c :-( In which case swapping the lines around may also help the compiler keep 'j' live. > + if (m > (u64)jiffies_to_usecs(MAX_JIFFY_OFFSET) * 1000) I think there's a problem with this line anyway. In kernel/time/time.c: // Warning! Result type may be narrower than parameter type - DSG unsigned int jiffies_to_usecs(const unsigned long j) { #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ) return (USEC_PER_SEC / HZ) * j; #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC) return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC); #else # if BITS_PER_LONG == 32 return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32; # else return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN; # endif #endif } Also, include/linux/jiffies.h: #define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1) and include/linux/kernel.h: #define LONG_MAX ((long)(~0UL>>1)) So, on a 64-bit build we'll have LONG_MAX == 0x7fff_ffff_ffff_ffff and MAX_JIFFY_OFFSET == 0x3fff_ffff_ffff_fffe. Multiplying that by 1000 gives an answer that doesn't fit in an unsigned int! Even on a 32-bit build (where LONG_MAX == 0x7fff_ffff and MAX_JIFFY_OFFSET == 0x3fff_fffe) MAX_JIFFY_OFFSET can't be multiplied by any typical value of HZ (50, 60, 1000) without overflow! I think the only way to get this right, give the somewhat broken nature of the kernel function signatures and its lack of a u64 jiffies-to-nsecs function, is to convert ONE jiffy to (unsigned int) usecs, then widen to u64 before converting to nsecs and using that for the rest of the calculations. .Dave. > + return MAX_JIFFY_OFFSET; > + > + return min_t(unsigned long, MAX_JIFFY_OFFSET, j + 1); > +} _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
