The following commit has been merged into the locking/core branch of tip: Commit-ID: 859d069ee1ddd87862e1d6a356a82ed417dbeb67 Gitweb: https://git.kernel.org/tip/859d069ee1ddd87862e1d6a356a82ed417dbeb67 Author: Peter Zijlstra <[email protected]> AuthorDate: Wed, 27 May 2020 15:00:57 +02:00 Committer: Peter Zijlstra <[email protected]> CommitterDate: Fri, 10 Jul 2020 12:00:01 +02:00
lockdep: Prepare for NMI IRQ state tracking 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) <[email protected]> Reviewed-by: Ingo Molnar <[email protected]> Link: https://lkml.kernel.org/r/[email protected] --- kernel/locking/lockdep.c | 46 +++++++++++++++++++++++++++++++++++---- 1 file changed, 42 insertions(+), 4 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 29a8de4..d595623 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -395,7 +395,7 @@ void lockdep_init_task(struct task_struct *task) static __always_inline void lockdep_recursion_finish(void) { - if (WARN_ON_ONCE(--current->lockdep_recursion)) + if (WARN_ON_ONCE((--current->lockdep_recursion) & LOCKDEP_RECURSION_MASK)) current->lockdep_recursion = 0; } @@ -3646,7 +3646,16 @@ static void __trace_hardirqs_on_caller(void) */ 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(unsigned long ip) { 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(unsigned long ip) 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(unsigned long ip) { 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; /*
