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Message-ID: <604c8751-5269-de29-0b7f-b3e93b6df4ca@redhat.com> Date: Sun, 28 Apr 2019 20:27:54 -0400 From: Waiman Long <longman@...hat.com> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Will Deacon <will.deacon@....com>, Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, Linux List Kernel Mailing <linux-kernel@...r.kernel.org>, the arch/x86 maintainers <x86@...nel.org>, Davidlohr Bueso <dave@...olabs.net>, Tim Chen <tim.c.chen@...ux.intel.com>, huang ying <huang.ying.caritas@...il.com> Subject: Re: [PATCH-tip v7 00/20] locking/rwsem: Rwsem rearchitecture part 2 On 4/28/19 8:10 PM, Linus Torvalds wrote: > On Sun, Apr 28, 2019 at 4:12 PM Waiman Long <longman@...hat.com> wrote: >> I implemented your suggestion in patch 1 as it will produce simpler and >> faster code. However, one of the changes in my patchset is to wake up >> all the readers in the wait list. This means I have to jump over the >> writers and wake up the readers behind them as well. See patch 11 for >> details. As a result, I have to revert back to use list_add_tail() and >> list_for_each_entry_safe() for the first pass. That is why the diff for >> the whole patchset is just the below change. It is done on purpose, not >> an omission. > Ahh, ok. In that case I suspect the clever code isn't even worth it, > since it very much depends on just splitting the list in a fixed > place. > > Linus Not really, this is a serious problem that have to be backported to earlier stable releases and downstream. The clever code is helpful in those cases. Cheers, Longman
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