From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from galois.linutronix.de ([193.142.43.55]) by casper.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kCjL9-0006UR-O5 for kexec@lists.infradead.org; Mon, 31 Aug 2020 12:55:17 +0000 From: John Ogness Subject: Re: [PATCH next v3 6/8] printk: ringbuffer: add finalization/extension support In-Reply-To: <20200831011058.6286-7-john.ogness@linutronix.de> References: <20200831011058.6286-1-john.ogness@linutronix.de> <20200831011058.6286-7-john.ogness@linutronix.de> Date: Mon, 31 Aug 2020 15:00:58 +0206 Message-ID: <878sdvq8kd.fsf@jogness.linutronix.de> MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Petr Mladek Cc: Andrea Parri , Sergey Senozhatsky , Paul McKenney , Peter Zijlstra , Greg Kroah-Hartman , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Steven Rostedt , Sergey Senozhatsky , Thomas Gleixner , Linus Torvalds This critical piece was missing from patch 6... >From 0b745d507f0c38e6d1612ed9468aa52845ca025b Mon Sep 17 00:00:00 2001 From: John Ogness Date: Mon, 31 Aug 2020 14:45:40 +0206 Subject: [PATCH] printk: ringbuffer: allow reading consistent descriptors desc_read() will fail to read if a descriptor is in the desc_reserved queried state because such data would be inconsistent. However, since ("printk: ringbuffer: add finalization/extension support") the desc_reserved state can have the DESC_COMMIT_MASK flag set, in which case it _is_ consistent. And indeed, desc_reopen_last() is expecting a read in this case. Allow desc_read() to read desc_reserved descriptors if the DESC_COMMIT_MASK flag is set. Signed-off-by: John Ogness Reported-by: Andy Lavr Fixes: ("printk: ringbuffer: add finalization/extension support") --- kernel/printk/printk_ringbuffer.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index 0731d5e2dddd..6ba7d3fc96f1 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -446,8 +446,10 @@ static enum desc_state desc_read(struct prb_desc_ring *desc_ring, /* Check the descriptor state. */ state_val = atomic_long_read(state_var); /* LMM(desc_read:A) */ d_state = get_desc_state(id, state_val); - if (d_state != desc_committed && d_state != desc_reusable) + if (d_state == desc_miss || + (d_state == desc_reserved && !(state_val & DESC_COMMIT_MASK))) { return d_state; + } /* * Guarantee the state is loaded before copying the descriptor -- 2.20.1 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec