Messages in this thread | | | Date | Thu, 19 Jan 2017 08:55:07 +0000 | From | Chris Wilson <> | Subject | Re: __mutex_lock_common() unlikely very likely |
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On Wed, Jan 18, 2017 at 03:58:24PM -0500, Steven Rostedt wrote: > Chris, > > My branch tracer flagged the unlikely in __mutex_lock_common() as > always hit. That's the: > > if (use_ww_ctx) { > [...] > if (unlikely(ww_ctx == READ_ONCE(ww->ctx))) > return -EALREADY; > } > > This is hit 100% of the time, and its coming from the drm logic:
By design this is an exceptional case. In practice, drm modesetting is a little slapsidasical when it comes to locking. However, it is the minority use case, just that on intel, the more prevalent users do not hit this path - though they will with the ww_mutex refactoring work. ttm drivers (amdgpu, nouveau etc) will be demonstrating that this is the unlikely branch. -Chris
-- Chris Wilson, Intel Open Source Technology Centre
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