On Tue, Jul 07, 2015 at 03:54:32AM -0700, tip-bot for Andy Lutomirski wrote: > Commit-ID: 0333a209cbf600e980fc55c24878a56f25f48b65 > Gitweb: http://git.kernel.org/tip/0333a209cbf600e980fc55c24878a56f25f48b65 > Author: Andy Lutomirski <l...@kernel.org> > AuthorDate: Fri, 3 Jul 2015 12:44:34 -0700 > Committer: Ingo Molnar <mi...@kernel.org> > CommitDate: Tue, 7 Jul 2015 10:59:10 +0200 > > x86/irq, context_tracking: Document how IRQ context tracking works and add an > RCU assertion > > Signed-off-by: Andy Lutomirski <l...@kernel.org> > Cc: Andy Lutomirski <l...@amacapital.net> > Cc: Borislav Petkov <b...@alien8.de> > Cc: Brian Gerst <brge...@gmail.com> > Cc: Denys Vlasenko <dvlas...@redhat.com> > Cc: Denys Vlasenko <vda.li...@googlemail.com> > Cc: Frederic Weisbecker <fweis...@gmail.com> > Cc: H. Peter Anvin <h...@zytor.com> > Cc: Kees Cook <keesc...@chromium.org> > Cc: Linus Torvalds <torva...@linux-foundation.org> > Cc: Oleg Nesterov <o...@redhat.com> > Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com> > Cc: Peter Zijlstra <pet...@infradead.org> > Cc: Rik van Riel <r...@redhat.com> > Cc: Thomas Gleixner <t...@linutronix.de> > Cc: paul...@linux.vnet.ibm.com > Link: > http://lkml.kernel.org/r/e8bdc4ed0193fb2fd130f3d6b7b8023e2ec1ab62.1435952415.git.l...@kernel.org > Signed-off-by: Ingo Molnar <mi...@kernel.org> > --- > arch/x86/kernel/irq.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c > index 88b36648..6233de0 100644 > --- a/arch/x86/kernel/irq.c > +++ b/arch/x86/kernel/irq.c > @@ -216,8 +216,23 @@ __visible unsigned int __irq_entry do_IRQ(struct pt_regs > *regs) > unsigned vector = ~regs->orig_ax; > unsigned irq; > > + /* > + * NB: Unlike exception entries, IRQ entries do not reliably > + * handle context tracking in the low-level entry code. This is > + * because syscall entries execute briefly with IRQs on before > + * updating context tracking state, so we can take an IRQ from > + * kernel mode with CONTEXT_USER. The low-level entry code only > + * updates the context if we came from user mode, so we won't > + * switch to CONTEXT_KERNEL. We'll fix that once the syscall > + * code is cleaned up enough that we can cleanly defer enabling > + * IRQs. > + */ > +
Now is it a problem to take interrupts in kernel mode with CONTEXT_USER? I'm not sure it's worth trying to make it not happen. > entering_irq(); > > + /* entering_irq() tells RCU that we're not quiescent. Check it. */ > + rcu_lockdep_assert(rcu_is_watching(), "IRQ failed to wake up RCU"); Why do we need to check that? > + > irq = __this_cpu_read(vector_irq[vector]); > > if (!handle_irq(irq, regs)) { Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/