From mboxrd@z Thu Jan 1 00:00:00 1970 From: mst@redhat.com (Michael S. Tsirkin) Date: Sun, 19 May 2013 16:34:18 +0300 Subject: [PATCH v2 10/10] kernel: might_fault does not imply might_sleep In-Reply-To: <1368966844.6828.111.camel@gandalf.local.home> References: <1f85dc8e6a0149677563a2dfb4cef9a9c7eaa391.1368702323.git.mst@redhat.com> <20130516184041.GP19669@dyad.programming.kicks-ass.net> <20130519093526.GD19883@redhat.com> <1368966844.6828.111.camel@gandalf.local.home> Message-ID: <20130519133418.GA24381@redhat.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Sun, May 19, 2013 at 08:34:04AM -0400, Steven Rostedt wrote: > On Sun, 2013-05-19 at 12:35 +0300, Michael S. Tsirkin wrote: > > > No, I was not assuming that. What I'm trying to say is that a caller > > that does something like this under a spinlock: > > preempt_disable > > pagefault_disable > > error = copy_to_user > > pagefault_enable > > preempt_enable_no_resched > > > > is not doing anything wrong and should not get a warning, > > as long as error is handled correctly later. > > Right? > > > > What I see wrong with the above is the preempt_enable_no_resched(). The > only place that should be ever used is right before a schedule(), as you > don't want to schedule twice (once for the preempt_enable() and then > again for the schedule itself). > > Remember, in -rt, a spin lock does not disable preemption. > > -- Steve Right but we need to keep it working on upstream as well. If I do preempt_enable under a spinlock upstream won't it try to sleep under spinlock? -- MST