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[2603:800c:1a02:1bae:a7fa:157f:969a:4cde]) by smtp.gmail.com with ESMTPSA id u11-20020a170902e80b00b0018996404dd5sm1741487plg.109.2022.11.30.09.00.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Nov 2022 09:00:18 -0800 (PST) Sender: Tejun Heo Date: Wed, 30 Nov 2022 07:00:17 -1000 From: Tejun Heo To: Linus Torvalds Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, joshdon@google.com, brho@google.com, pjt@google.com, derkling@google.com, haoluo@google.com, dvernet@meta.com, dschatzberg@meta.com, dskarlat@cs.cmu.edu, riel@surriel.com, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH 01/31] rhashtable: Allow rhashtable to be used from irq-safe contexts Message-ID: References: <20221130082313.3241517-1-tj@kernel.org> <20221130082313.3241517-2-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Wed, Nov 30, 2022 at 08:35:13AM -0800, Linus Torvalds wrote: > On Wed, Nov 30, 2022 at 12:23 AM Tejun Heo wrote: > > > > > > static inline void rht_lock(struct bucket_table *tbl, > > - struct rhash_lock_head __rcu **bkt) > > + struct rhash_lock_head __rcu **bkt, > > + unsigned long *flags) > > I guess it doesn't matter as long as this actually gets inlined, but > wouldn't it be better to have > > flags = rht_lock(..); > ... > rht_unlock(.., flags); > > as the calling convention? Rather than passing a pointer to the stack around. Sure thing. > That's what the native _raw_spin_lock_irqsave() interface is (even if > "spin_lock_irqsave()" itself for historical reasons uses that inline > asm-like "pass argument by reference *without* using a pointer") Yeah, it always feels kinda weird to wrap irqsave/restore due to the special reference passing. > And gaah, we should have made 'flags' be a real type long ago, but I > guess 'unsigned long' is too ingrained and traditional to change that > now. Hahaha, that's gonna be an epic patchset. Thanks. -- tejun