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[2001:8b0:10b:1231::1]) by mx.google.com with ESMTPS id h124si1267361jab.37.2019.05.30.01.04.09 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 30 May 2019 01:04:09 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of peterz@infradead.org designates 2001:8b0:10b:1231::1 as permitted sender) client-ip=2001:8b0:10b:1231::1; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=merlin.20170209 header.b=wxvteZMt; spf=pass (google.com: best guess record for domain of peterz@infradead.org designates 2001:8b0:10b:1231::1 as permitted sender) smtp.mailfrom=peterz@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=ZNHljSo+xuO+rijXANsB4tJFe4vq/fcU3WZ/qW7T1K4=; b=wxvteZMtqs4EUcTAMJWHqixz6 mFlqd2lJn4cAJwAR/hiRZrEL1HzdpfpSWviOKW76MazUqLmiCOX0GXm9QTDDGduA5qdqBmPAd1R7/ gtqvGkRUITnXCQaDqEVvt5XPaHTg+ZT+AMGLgBcwFJMbrTOd+9sLivPTHl8mHadihGFP0gX7iwini Q8Pj3wSK1+yjR342xlFv6RVYcZ+uBZY/cOmdfazWIwbFvd8oxQeWoMEc04vYPX77/yQa648a+tnc3 5OW0ffbHO3MaepHn+iCGQ4H+GGlo9+ea+OgZeFcCBAVm+/3fFP9eqtKq+q2nEJa3OQDIFlizD1mXZ w34kI7GWQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hWG2a-0004nX-GI; Thu, 30 May 2019 08:04:00 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id D70FB201B3992; Thu, 30 May 2019 10:03:58 +0200 (CEST) Date: Thu, 30 May 2019 10:03:58 +0200 From: Peter Zijlstra To: Qian Cai Cc: axboe@kernel.dk, akpm@linux-foundation.org, hch@lst.de, oleg@redhat.com, gkohli@codeaurora.org, mingo@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] block: fix a crash in do_task_dead() Message-ID: <20190530080358.GG2623@hirez.programming.kicks-ass.net> References: <1559161526-618-1-git-send-email-cai@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1559161526-618-1-git-send-email-cai@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, May 29, 2019 at 04:25:26PM -0400, Qian Cai wrote: > Fixes: 0619317ff8ba ("block: add polled wakeup task helper") What is the purpose of that patch ?! The Changelog doesn't mention any benefit or performance gain. So why not revert that? > Signed-off-by: Qian Cai > --- > include/linux/blkdev.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > index 592669bcc536..290eb7528f54 100644 > --- a/include/linux/blkdev.h > +++ b/include/linux/blkdev.h > @@ -1803,7 +1803,7 @@ static inline void blk_wake_io_task(struct task_struct *waiter) > * that case, we don't need to signal a wakeup, it's enough to just > * mark us as RUNNING. > */ > - if (waiter == current) > + if (waiter == current && in_task()) > __set_current_state(TASK_RUNNING); NAK, No that's broken too. The right fix is something like: if (waiter == current) { barrier(); if (current->state & TASK_NORAL) __set_current_state(TASK_RUNNING); } But even that is yuck to do outside of the scheduler code, as it looses tracepoints and stats. So can we please just revert that original patch and start over -- if needed? > else > wake_up_process(waiter); > -- > 1.8.3.1 >