From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Petazzoni Date: Fri, 15 Jun 2018 19:27:26 +0000 Subject: Re: [PATCH] arch/sh: use slow path for get_user_pages_fast() on SMP Message-Id: <20180615212726.17d8ffe5@windsurf> List-Id: References: <20180615155237.8166-1-thomas.petazzoni@bootlin.com> <474bbdcc-d78f-faa0-b2c3-3650cc870b36@cogentembedded.com> In-Reply-To: <474bbdcc-d78f-faa0-b2c3-3650cc870b36@cogentembedded.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Sergei Shtylyov Cc: Yoshinori Sato , Rich Felker , linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org Hello, On Fri, 15 Jun 2018 19:04:45 +0300, Sergei Shtylyov wrote: > Hello! > > On 06/15/2018 06:52 PM, Thomas Petazzoni wrote: > > > The fast path of get_user_pages_fast() disables IRQs and then does: > > > > - gup_pud_range() > > - gup_pmd_range() > > - gup_pte_range() > > - flush_dcache_page() > > > > However, flush_dcache_page() makes a smp_call_function(), and using > > smp_call_function() when IRQs are disabled is not allowed. > > > > In order to work around this problem, this commit prevents the fast > > path from get_user_pages_fast() from being used on SMP, and directly > ^^^^ of? > Else it sounds a bit tautological... I re-read again my sentence, and I believe it's correct and it has the meaning I intended to give. Of course, I'm not a native english speaker, so I might be wrong on this :-) I'm actually more interested in hearing whether there is a better solution to this problem. This patch submission is really a very proposal, and I'm hoping to get some better suggestions on how to approach the problem. Best regards, Thomas -- Thomas Petazzoni, CTO, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com