Messages in this thread Patch in this message | | | Date | Fri, 29 May 2020 23:27:41 +0200 | From | Peter Zijlstra <> | Subject | [PATCH 13/14] lockdep: Prepare for NMI IRQ state tracking |
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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) <peterz@infradead.org> --- kernel/locking/lockdep.c | 33 ++++++++++++++++++++++++++++++--- 1 file changed, 30 insertions(+), 3 deletions(-)
--- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -3646,7 +3646,13 @@ static void __trace_hardirqs_on_caller(v */ void lockdep_hardirqs_on_prepare(unsigned long ip) { - if (unlikely(!debug_locks || current->lockdep_recursion)) + /* + * NMIs do not (and cannot) track lock dependencies, nothing to do. + */ + if (in_nmi()) + return; + + if (DEBUG_LOCKS_WARN_ON(current->lockdep_recursion & LOCKDEP_RECURSION_MASK)) return; if (unlikely(current->hardirqs_enabled)) { @@ -3692,7 +3698,24 @@ void noinstr lockdep_hardirqs_on(unsigne { struct task_struct *curr = current; - if (unlikely(!debug_locks || curr->lockdep_recursion)) + /* + * 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 (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 (DEBUG_LOCKS_WARN_ON(curr->lockdep_recursion & LOCKDEP_RECURSION_MASK)) return; if (curr->hardirqs_enabled) { @@ -3720,6 +3743,7 @@ 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 +3759,10 @@ void noinstr lockdep_hardirqs_off(unsign { struct task_struct *curr = current; - if (unlikely(!debug_locks || curr->lockdep_recursion)) + /* + * NMIs can happen in lockdep. + */ + if (!in_nmi() && DEBUG_LOCKS_WARN_ON(curr->lockdep_recursion & LOCKDEP_RECURSION_MASK)) return; /*
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