From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexey.Brodkin@synopsys.com (Alexey Brodkin) Date: Fri, 16 Mar 2018 15:01:22 +0000 Subject: Do we need to disable preemption in flush_tlb_range()? In-Reply-To: <20180316101124.GB4064@hirez.programming.kicks-ass.net> References: <1519917189.13866.6.camel@synopsys.com> <5a5c67c1-9f45-f908-2c8d-0914cd616a18@synopsys.com> <20180315082720.GT4064@hirez.programming.kicks-ass.net> <1521106770.11552.70.camel@synopsys.com> <20180316101124.GB4064@hirez.programming.kicks-ass.net> List-ID: Message-ID: <1521212481.4805.2.camel@synopsys.com> To: linux-snps-arc@lists.infradead.org Hi Peter, On Fri, 2018-03-16@11:11 +0100, Peter Zijlstra wrote: > On Thu, Mar 15, 2018@09:39:31AM +0000, Alexey Brodkin wrote: > > Hi Peter, > > > > On Thu, 2018-03-15@09:27 +0100, Peter Zijlstra wrote: > > > On Wed, Mar 14, 2018@01:19:01PM -0700, Vineet Gupta wrote: > > > > +CC Peter since we have his attention ;-) > > > > > > Yeah, timezone collision there, I typically sleep at 1am ;-) > > > > > > > On 03/01/2018 07:13 AM, Alexey Brodkin wrote: > > > > > Hi Vineet, > > > > > > > > > > Just noticed that in comments for smp_call_function_many() it is said that > > > > > preemption must be disabled during its execution. And that function gets executed > > > > > among other ways like that: > > > > > -------------------------->8----------------------- > > > > > flush_tlb_range() > > > > > -> on_each_cpu_mask() > > > > > -> smp_call_function_many() > > > > > -------------------------->8----------------------- > > > > > > > > In general I prefer not to - Peter what say you ? > > > > > > The comment with smp_call_function_many() is correct, it relies on > > > preemption being disabled in a number of ways. I would expect > > > this_cpu_ptr() for example to complain when used with preemption > > > enabled (CONFIG_DEBUG_PREEMPT). > > So on_each_cpu_mask() already disables preemption around calling > smp_call_function_many(). Right that happens in get_cpu() so then we're golden here. Thanks for pointing out - was not clear immediately from the code :) -Alexey