Messages in this thread Patch in this message | | | Date | Tue, 7 Jul 2015 03:54:32 -0700 | From | tip-bot for Andy Lutomirski <> | Subject | [tip:x86/asm] x86/irq, context_tracking: Document how IRQ context tracking works and add an RCU assertion |
| |
Commit-ID: 0333a209cbf600e980fc55c24878a56f25f48b65 Gitweb: http://git.kernel.org/tip/0333a209cbf600e980fc55c24878a56f25f48b65 Author: Andy Lutomirski <luto@kernel.org> AuthorDate: Fri, 3 Jul 2015 12:44:34 -0700 Committer: Ingo Molnar <mingo@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 <luto@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: paulmck@linux.vnet.ibm.com Link: http://lkml.kernel.org/r/e8bdc4ed0193fb2fd130f3d6b7b8023e2ec1ab62.1435952415.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@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. + */ + 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"); + irq = __this_cpu_read(vector_irq[vector]); if (!handle_irq(irq, regs)) {
| |