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Mon, 30 Mar 2026 06:51:00 -0700 (PDT) Message-ID: Date: Mon, 30 Mar 2026 21:50:56 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] crypto: jitterentropy - replace long-held spinlock with mutex To: Herbert Xu Cc: linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, davem@davemloft.net, smueller@chronox.de, yifanwucs@gmail.com, tomapufckgml@gmail.com, yuantan098@gmail.com, bird@lzu.edu.cn References: <9a8ef1cbcc68b752a495acf0a23e7095eb0a7796.1774854094.git.jerryxucs@gmail.com> Content-Language: en-US From: Haixin Xu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Herbert, On 3/30/26 16:51, Herbert Xu wrote: > Are you sure that this function never gets called from softirq > context? Yes, for this implementation and its current call paths, I believe using a mutex here is safe. As `jitterentropy_rng` is not used as the generic `crypto_default_rng` directly, i found only two users of it in tree: 1. AF_ALG RNG sockets via crypto/algif_rng.c `_rng_recvmsg()` calls `crypto_rng_generate()` from the calling task's syscall context. 2. DRBG seeding via crypto/drbg.c `drbg_seed()` calls `crypto_rng_get_bytes()`, `dbrg_seed()` requires holding `drbg->drbg_mutex`. There are also other RNG implementations in tree that hold a mutex in the generate function. For example: - crypto/drbg.c uses `drbg->drbg_mutex` in `drbg_generate_long` - drivers/crypto/qcom-rng.c uses `rng->lock` in `qcom_rng_generate` So my reasoning is that using a mutex here should be safe. Best regards Haixin Xu