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Fri, 10 Jul 2020 01:47:46 -0700 (PDT) From: Sergey Senozhatsky X-Google-Original-From: Sergey Senozhatsky Date: Fri, 10 Jul 2020 17:47:44 +0900 To: Sergey Senozhatsky Cc: John Ogness , Petr Mladek , Peter Zijlstra , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Andrea Parri , Thomas Gleixner , Paul McKenney , kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 2/4] printk: add lockless ringbuffer Message-ID: <20200710084744.GA488397@jagdpanzerIV.localdomain> References: <20200709132344.760-1-john.ogness@linutronix.de> <20200709132344.760-3-john.ogness@linutronix.de> <20200710084305.GA144760@jagdpanzerIV.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200710084305.GA144760@jagdpanzerIV.localdomain> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (20/07/10 17:43), Sergey Senozhatsky wrote: > [..] > > > +void prb_init(struct printk_ringbuffer *rb, > > + char *text_buf, unsigned int textbits, > > + char *dict_buf, unsigned int dictbits, > > + struct prb_desc *descs, unsigned int descbits) > > +{ > > + memset(descs, 0, _DESCS_COUNT(descbits) * sizeof(descs[0])); > > + > > + rb->desc_ring.count_bits = descbits; > > + rb->desc_ring.descs = descs; > > + atomic_long_set(&rb->desc_ring.head_id, DESC0_ID(descbits)); > > + atomic_long_set(&rb->desc_ring.tail_id, DESC0_ID(descbits)); > > + > > + rb->text_data_ring.size_bits = textbits; > > + rb->text_data_ring.data = text_buf; > > + atomic_long_set(&rb->text_data_ring.head_lpos, BLK0_LPOS(textbits)); > > + atomic_long_set(&rb->text_data_ring.tail_lpos, BLK0_LPOS(textbits)); > > + > > + rb->dict_data_ring.size_bits = dictbits; > > + rb->dict_data_ring.data = dict_buf; > > + atomic_long_set(&rb->dict_data_ring.head_lpos, BLK0_LPOS(dictbits)); > > + atomic_long_set(&rb->dict_data_ring.tail_lpos, BLK0_LPOS(dictbits)); > > + > > Just a side note: some people want !CONFIG_PRINTK builds. I wonder > how many people will want !CONFIG_PRINTK_DICT. The core logbuf/dict > logbuf split is really cool. We also may be can add a dedicated logbuf for the user-space logs, as opposed to current "user space can write to the kernel logbuf". Some folks really dislike that systemd, for instance, can trash the core kernel logbuf doing a lot of /dev/kmsg writes. -ss