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Fri, 06 Sep 2019 03:09:47 -0700 (PDT) Date: Fri, 6 Sep 2019 19:09:43 +0900 From: Sergey Senozhatsky To: Peter Zijlstra Cc: Petr Mladek , John Ogness , Andrea Parri , Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Brendan Higgins , Thomas Gleixner , Linus Torvalds , Greg Kroah-Hartman , linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v4 0/9] printk: new ringbuffer implementation Message-ID: <20190906100943.GB10876@jagdpanzerIV> References: <20190807222634.1723-1-john.ogness@linutronix.de> <20190904123531.GA2369@hirez.programming.kicks-ass.net> <20190905130513.4fru6yvjx73pjx7p@pathway.suse.cz> <20190905143118.GP2349@hirez.programming.kicks-ass.net> <20190906090627.GX2386@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190906090627.GX2386@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (09/06/19 11:06), Peter Zijlstra wrote: > Another approach is something like: > > DEFINE_PER_CPU(int, printk_nest); > DEFINE_PER_CPU(char, printk_line[4][256]); > > int vprintk(const char *fmt, va_list args) > { > int c, n, i; > char *buf; > > preempt_disable(); > i = min(3, this_cpu_inc_return(printk_nest) - 1); > buf = this_cpu_ptr(printk_line[i]); > n = vscnprintf(buf, 256, fmt, args); > > c = cpu_lock(); > printk_buffer_store(buf, n); > if (early_console) > early_console->write(early_console, buf, n); > cpu_unlock(c); > > this_cpu_dec(printk_nest); > preempt_enable(); > > return n; > } > > Again, simple and straight forward (and I'm sure it's been mentioned > before too). :) --- diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c index 139c310049b1..9c73eb6259ce 100644 --- a/kernel/printk/printk_safe.c +++ b/kernel/printk/printk_safe.c @@ -103,7 +103,10 @@ static __printf(2, 0) int printk_safe_log_store(struct printk_safe_seq_buf *s, if (atomic_cmpxchg(&s->len, len, len + add) != len) goto again; - queue_flush_work(s); + if (early_console) + early_console->write(early_console, s->buffer + len, add); + else + queue_flush_work(s); return add; } --- -ss