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Thu, 11 Sep 2025 08:58:49 -0700 (PDT) Received: from pathway.suse.cz ([176.114.240.130]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b07b32dd6f3sm158238666b.67.2025.09.11.08.58.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Sep 2025 08:58:49 -0700 (PDT) Date: Thu, 11 Sep 2025 17:58:47 +0200 From: Petr Mladek To: Daniil Tatianin Cc: linux-kernel@vger.kernel.org, Steven Rostedt , John Ogness , Sergey Senozhatsky Subject: Re: [PATCH v2 0/2] printk_ringbuffer: don't needlessly wrap data blocks around Message-ID: References: <20250905144152.9137-1-d-tatianin@yandex-team.ru> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu 2025-09-11 17:30:36, Petr Mladek wrote: > On Fri 2025-09-05 17:41:50, Daniil Tatianin wrote: > > This series fixes the issue where data blocks would wrap in cases where the last > > data block perfectly fits the ring. This caused whatever was at the beginning of > > the ring to get discarded in this case, and the data block would get put there > > even though it could be put at the end of the data ring just fine without > > discarding anything. > > > > Fixing this issue also allows to simplify the check in data_check_size, > > previously it would ensure there's space for a trailing id, which we > > don't need anymore. > > > > v0->v1: > > - Fix severely broken code alignment > > > > v1->v2: > > - Rename & invert get_next_lpos -> is_blk_wrapped > > - Add a new commit for changing the logic in data_check_size > > The patchset looks good to me. But I wanted to do some tests > and it failed. I did the following: > > 1. Applied this patchset on top of printk/linux.git, branch for-next, > https://git.kernel.org/pub/scm/linux/kernel/git/printk/linux.git/log/?h=for-next > > I this branch because it contains a new KUnit test for the printk > ring buffer. I forgot the add the patch: diff --git a/kernel/printk/printk_ringbuffer_kunit_test.c b/kernel/printk/printk_ringbuffer_kunit_test.c index 2282348e869a..241f7ef49ac6 100644 --- a/kernel/printk/printk_ringbuffer_kunit_test.c +++ b/kernel/printk/printk_ringbuffer_kunit_test.c @@ -56,7 +56,7 @@ struct prbtest_rbdata { char text[] __counted_by(size); }; -#define MAX_RBDATA_TEXT_SIZE 0x80 +#define MAX_RBDATA_TEXT_SIZE (0x256 - sizeof(struct prbtest_rbdata)) #define MAX_PRB_RECORD_SIZE (sizeof(struct prbtest_rbdata) + MAX_RBDATA_TEXT_SIZE) struct prbtest_data { @@ -251,7 +251,7 @@ static inline void prbtest_prb_reinit(struct printk_ringbuffer *rb) static void test_readerwriter(struct kunit *test) { /* Equivalent to CONFIG_LOG_BUF_SHIFT=13 */ - DEFINE_PRINTKRB(test_rb, 8, 5); + DEFINE_PRINTKRB(test_rb, 4, 4); struct prbtest_thread_data *thread_data; struct prbtest_data *test_data; -- 2.51.0 Best Regards, Petr