Path: csiph.com!aioe.org!news.lightlink.com!eternal-september.org!feeder.eternal-september.org!weretis.net!feeder4.news.weretis.net!newsfeed.datemas.de!news.albasani.net!tahina.priv.at!bofh.it!news.nic.it!robomod From: Andy Lutomirski Newsgroups: linux.kernel Subject: [PATCH v3 15/15] x86/irq: Document how IRQ context tracking works and add an assertion Date: Wed, 24 Jun 2015 04:50:03 +0200 Message-ID: References: X-Original-To: x86@kernel.org, linux-kernel@vger.kernel.org X-Mailer: git-send-email 2.4.3 Sender: robomod@news.nic.it List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Approved: robomod@news.nic.it Lines: 41 Organization: linux.* mail to news gateway X-Original-Cc: =?UTF-8?q?Fr=C3=A9d=C3=A9ric=20Weisbecker?= , Rik van Riel , Oleg Nesterov , Denys Vlasenko , Borislav Petkov , Kees Cook , Brian Gerst , paulmck@linux.vnet.ibm.com, Andy Lutomirski X-Original-Date: Tue, 23 Jun 2015 19:46:18 -0700 X-Original-Message-ID: <5170d3b1685fe420a8265e70d65e8c354e8b683a.1435113808.git.luto@kernel.org> X-Original-References: X-Original-Sender: linux-kernel-owner@vger.kernel.org Xref: aioe.org linux.kernel:1171055 Signed-off-by: Andy Lutomirski --- 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 88b366487b0e..6233de046c08 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)) { -- 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/