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[2003:d8:2f25:9c00:e2c7:6eb5:8a51:1c60]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-447f6f05581sm73492495e9.13.2025.05.21.08.40.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 21 May 2025 08:40:08 -0700 (PDT) Message-ID: <6ce8f663-2bcc-43a0-bbd8-71fc36005e86@redhat.com> Date: Wed, 21 May 2025 17:40:07 +0200 Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9] mm/mempolicy: Weighted Interleave Auto-tuning To: Joshua Hahn Cc: gourry@gourry.net, akpm@linux-foundation.org, harry.yoo@oracle.com, ying.huang@linux.alibaba.com, honggyu.kim@sk.com, yunjeong.mun@sk.com, gregkh@linuxfoundation.org, rakie.kim@sk.com, rafael@kernel.org, lenb@kernel.org, dan.j.williams@intel.com, Jonathan.Cameron@huawei.com, dave.jiang@intel.com, horen.chuang@linux.dev, hannes@cmpxchg.org, osalvador@suse.de, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com References: <20250521153730.2196701-1-joshua.hahnjy@gmail.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 21.05.25 17:37, Joshua Hahn wrote: > On Wed, 21 May 2025 15:04:00 +0200 David Hildenbrand wrote: > >> On 20.05.25 16:12, Joshua Hahn wrote: > > [...snip...] > >> [...] >> >>> -static void iw_table_free(void) >>> +static void wi_state_free(void) >>> { >>> - u8 *old; >>> + struct weighted_interleave_state *old_wi_state; >>> >>> - mutex_lock(&iw_table_lock); >>> - old = rcu_dereference_protected(iw_table, >>> - lockdep_is_held(&iw_table_lock)); >>> - rcu_assign_pointer(iw_table, NULL); >>> - mutex_unlock(&iw_table_lock); >>> + mutex_lock(&wi_state_lock); >>> + >>> + old_wi_state = rcu_dereference_protected(wi_state, >>> + lockdep_is_held(&wi_state_lock)); >>> + if (!old_wi_state) { >>> + mutex_unlock(&wi_state_lock); >>> + goto out; >>> + } >>> >>> + rcu_assign_pointer(wi_state, NULL); >>> + mutex_unlock(&wi_state_lock); >> >> Just one nit: if written as: >> >> ... >> rcu_assign_pointer(wi_state, NULL); >> mutex_unlock(&wi_state_lock); >> >> old_wi_state = ... >> if (old_wi_state) { >> synchronize_rcu(); >> kfree(old_wi_state); >> } >> kfree(&wi_group->wi_kobj); >> >> You can easily avoid the goto. > > Ah I see, thank you for the suggestion! > I think we would have to move the "old_wi_state = ..." to be inside > the lock and before the rcu_assign_pointer since wi_state will be > NULL at that point if we do not, but other than that, I think this > is a great optimization over the version I have : -) > > I will send in a fix patch for this later as a cleanup patch, if > that sounds good with you! Sure, you can do a cleanup on top. -- Cheers, David / dhildenb