On Tue, Aug 7, 2018 at 6:55 PM, Steven Rostedt <rost...@goodmis.org> wrote: > On Tue, 7 Aug 2018 18:17:42 -0700 > Joel Fernandes <joe...@google.com> wrote: > >> From 6986af946ceb04fc9ddc6d5b45fc559b6807e465 Mon Sep 17 00:00:00 2001 >> From: "Joel Fernandes (Google)" <j...@joelfernandes.org> >> Date: Sun, 5 Aug 2018 20:17:41 -0700 >> Subject: [PATCH] tracepoint: Run tracepoints even after CPU is offline >> >> Commit f37755490fe9 ("tracepoints: Do not trace when cpu is offline") >> causes a problem for lockdep using tracepoint code. Once a CPU is >> offline, tracepoints donot get called, however this causes a big problem >> for lockdep probes that need to run so that IRQ annotations are marked >> correctly. >> >> A race is possible where while the CPU is going offline, an interrupt >> can come in and then a lockdep assert causes an annotation warning: >> >> [ 106.551354] IRQs not enabled as expected >> [ 106.551785] WARNING: CPU: 1 PID: 0 at kernel/time/tick-sched.c:982 >> tick_nohz_idle_enter+0x99/0xb0 >> [ 106.552964] Modules linked in: >> [ 106.553299] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G W >> >> We need tracepoints to run as late as possible. This commit fixes the >> issue by removing the cpu_online check in tracepoint code that was >> introduced in the mentioned commit, however we now switch to using SRCU >> for all tracepoints and special handle calling tracepoints from NMI so >> that we don't run into issues that result from using sched-RCU when the >> CPUs are marked to be offline. >> >> Fixes: c3bc8fd637a9 ("tracing: Centralize preemptirq tracepoints and >> unify their usage") >> Reported-by: Masami Hiramatsu <mhira...@kernel.org> >> Signed-off-by: Joel Fernandes (Google) <j...@joelfernandes.org> > > > The above change log doesn't look like it matches the NMI patch. > > Can you resend with just the NMI changes? I already handled the cpu > offline ones.
Ok, sent with "cpu offline" changes dropped, here it is: https://lore.kernel.org/patchwork/patch/972657/ If you could add your Reported-by to it, that would be great as well. > > But I may still have concerns with this patch. Ok let me know what you think. Thanks! - Joel