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Ts'o" , Oleg Nesterov , Amir Goldstein , Jan Kara , Matthew Wilcox References: <1526405884-4860-1-git-send-email-longman@redhat.com> <1526405884-4860-3-git-send-email-longman@redhat.com> <20180515175805.GN12217@hirez.programming.kicks-ass.net> <1baa1a1a-a4a7-d706-8c01-5ff6a8757f97@redhat.com> <20180515180549.GP12217@hirez.programming.kicks-ass.net> From: Waiman Long Organization: Red Hat Message-ID: Date: Tue, 15 May 2018 14:35:33 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20180515180549.GP12217@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-fsdevel-owner@vger.kernel.org X-Mailing-List: linux-fsdevel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 05/15/2018 02:05 PM, Peter Zijlstra wrote: > On Tue, May 15, 2018 at 02:02:00PM -0400, Waiman Long wrote: >> On 05/15/2018 01:58 PM, Peter Zijlstra wrote: >>> On Tue, May 15, 2018 at 01:38:04PM -0400, Waiman Long wrote: >>>> +/* >>>> + * Owner value to indicate the rwsem's owner is not currently known. >>>> + */ >>>> +#define RWSEM_OWNER_UNKNOWN ((struct task_struct *)-1) >>> It might be nice to comment that this works and relies on having that >>> ANON_OWNER bit set. >> I am just trying not to expose internal working of rwsem, but I can >> document that one of the bits is the real deal without specifying which one. > Thing is, you don't want someone changing this without knowing about > that one magic bit. It doesn't hurt to be explicit here. > > Also, do we want -1L instead of a -1 literal? > Yes, I should -1L instead. Cheers, Longman