diff options
| author | Dave Gordon <david.s.gordon@intel.com> | 2016-09-14 13:10:33 +0100 |
|---|---|---|
| committer | Chris Wilson <chris@chris-wilson.co.uk> | 2016-09-15 10:48:40 +0100 |
| commit | b0876afdff45a4714e11f18ebbfb81762b417eac (patch) | |
| tree | 085f5826718664a74ee7cafd266bfc3950dcc80d /drivers/gpu/drm/i915/intel_drv.h | |
| parent | c8ebfad7a063fe665417fa0eeb0da7cfe987d8ed (diff) | |
drm/i915: Only expand COND once in wait_for()
Commentary from Chris Wilson's original version:
> I was looking at some wait_for() timeouts on a slow system, with lots of
> debug enabled (KASAN, lockdep, mmio_debug). Thinking that we were
> mishandling the timeout, I tried to ensure that we loop at least once
> after first testing COND. However, the double test of COND either side
> of the timeout check makes that unlikely. But we can do an equivalent
> loop, that keeps the COND check after testing for timeout (required so
> that we are not preempted between testing COND and then testing for a
> timeout) without expanding COND twice.
>
> The advantage of only expanding COND once is a dramatic reduction in
> code size:
>
> text data bss dec hex
> 1308733 5184 1152 1315069 1410fd before
> 1305341 5184 1152 1311677 1403bd after
but it turned out that due to a missing iniitialiser, gcc had "gone
wild trimming undefined code" :( This version acheives a rather more
modest (but still worthwhile) gain of ~550 bytes.
Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
Original-idea-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Zanoni, Paulo R <paulo.r.zanoni@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1473855033-26980-1-git-send-email-david.s.gordon@intel.com
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Diffstat (limited to 'drivers/gpu/drm/i915/intel_drv.h')
| -rw-r--r-- | drivers/gpu/drm/i915/intel_drv.h | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h index 7700e3254b26..810c89eb6863 100644 --- a/drivers/gpu/drm/i915/intel_drv.h +++ b/drivers/gpu/drm/i915/intel_drv.h @@ -52,11 +52,15 @@ */ #define _wait_for(COND, US, W) ({ \ unsigned long timeout__ = jiffies + usecs_to_jiffies(US) + 1; \ - int ret__ = 0; \ - while (!(COND)) { \ - if (time_after(jiffies, timeout__)) { \ - if (!(COND)) \ - ret__ = -ETIMEDOUT; \ + int ret__; \ + for (;;) { \ + bool expired__ = time_after(jiffies, timeout__); \ + if (COND) { \ + ret__ = 0; \ + break; \ + } \ + if (expired__) { \ + ret__ = -ETIMEDOUT; \ break; \ } \ if ((W) && drm_can_sleep()) { \ |