From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56478 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731903AbgFWIjZ (ORCPT ); Tue, 23 Jun 2020 04:39:25 -0400 Message-ID: <20200623083721.155449112@infradead.org> Date: Tue, 23 Jun 2020 10:36:46 +0200 From: Peter Zijlstra Subject: [PATCH v4 1/8] lockdep: Prepare for NMI IRQ state tracking References: <20200623083645.277342609@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-s390-owner@vger.kernel.org List-ID: To: mingo@kernel.org, will@kernel.org, tglx@linutronix.de Cc: x86@kernel.org, linux-kernel@vger.kernel.org, a.darwish@linutronix.de, rostedt@goodmis.org, bigeasy@linutronix.de, peterz@infradead.org, davem@davemloft.net, sparclinux@vger.kernel.org, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, heiko.carstens@de.ibm.com, linux-s390@vger.kernel.org, linux@armlinux.org.uk There is no reason not to always, accurately, track IRQ state. This change also makes IRQ state tracking ignore lockdep_off(). Signed-off-by: Peter Zijlstra (Intel) --- kernel/locking/lockdep.c | 44 +++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 41 insertions(+), 3 deletions(-) --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -3646,7 +3646,16 @@ static void __trace_hardirqs_on_caller(v */ void lockdep_hardirqs_on_prepare(unsigned long ip) { - if (unlikely(!debug_locks || current->lockdep_recursion)) + if (unlikely(!debug_locks)) + return; + + /* + * NMIs do not (and cannot) track lock dependencies, nothing to do. + */ + if (unlikely(in_nmi())) + return; + + if (unlikely(current->lockdep_recursion & LOCKDEP_RECURSION_MASK)) return; if (unlikely(current->hardirqs_enabled)) { @@ -3692,7 +3701,27 @@ void noinstr lockdep_hardirqs_on(unsigne { struct task_struct *curr = current; - if (unlikely(!debug_locks || curr->lockdep_recursion)) + if (unlikely(!debug_locks)) + return; + + /* + * NMIs can happen in the middle of local_irq_{en,dis}able() where the + * tracking state and hardware state are out of sync. + * + * NMIs must save lockdep_hardirqs_enabled() to restore IRQ state from, + * and not rely on hardware state like normal interrupts. + */ + if (unlikely(in_nmi())) { + /* + * Skip: + * - recursion check, because NMI can hit lockdep; + * - hardware state check, because above; + * - chain_key check, see lockdep_hardirqs_on_prepare(). + */ + goto skip_checks; + } + + if (unlikely(current->lockdep_recursion & LOCKDEP_RECURSION_MASK)) return; if (curr->hardirqs_enabled) { @@ -3720,6 +3749,7 @@ void noinstr lockdep_hardirqs_on(unsigne DEBUG_LOCKS_WARN_ON(current->hardirq_chain_key != current->curr_chain_key); +skip_checks: /* we'll do an OFF -> ON transition: */ curr->hardirqs_enabled = 1; curr->hardirq_enable_ip = ip; @@ -3735,7 +3765,15 @@ void noinstr lockdep_hardirqs_off(unsign { struct task_struct *curr = current; - if (unlikely(!debug_locks || curr->lockdep_recursion)) + if (unlikely(!debug_locks)) + return; + + /* + * Matching lockdep_hardirqs_on(), allow NMIs in the middle of lockdep; + * they will restore the software state. This ensures the software + * state is consistent inside NMIs as well. + */ + if (unlikely(!in_nmi() && (current->lockdep_recursion & LOCKDEP_RECURSION_MASK))) return; /*