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authorLinus Torvalds <torvalds@linux-foundation.org>2020-11-29 11:19:26 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2020-11-29 11:19:26 -0800
commitf91a3aa6bce480fe6e08df540129f4a923222419 (patch)
treee8a9063323abbd850adebbd4f1d50b5d51364e5f /kernel
parent8b7a51ba2637ee53ce90624f5f98aaf8ec9b2bcc (diff)
parent6e1d2bc675bd57640f5658a4a657ae488db4c204 (diff)
Merge tag 'locking-urgent-2020-11-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Thomas Gleixner: "Two more places which invoke tracing from RCU disabled regions in the idle path. Similar to the entry path the low level idle functions have to be non-instrumentable" * tag 'locking-urgent-2020-11-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: intel_idle: Fix intel_idle() vs tracing sched/idle: Fix arch_cpu_idle() vs tracing
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched/idle.c28
1 files changed, 27 insertions, 1 deletions
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 24d0ee26377d..c6932b8f4467 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -78,7 +78,7 @@ void __weak arch_cpu_idle_dead(void) { }
void __weak arch_cpu_idle(void)
{
cpu_idle_force_poll = 1;
- local_irq_enable();
+ raw_local_irq_enable();
}
/**
@@ -94,9 +94,35 @@ void __cpuidle default_idle_call(void)
trace_cpu_idle(1, smp_processor_id());
stop_critical_timings();
+
+ /*
+ * arch_cpu_idle() is supposed to enable IRQs, however
+ * we can't do that because of RCU and tracing.
+ *
+ * Trace IRQs enable here, then switch off RCU, and have
+ * arch_cpu_idle() use raw_local_irq_enable(). Note that
+ * rcu_idle_enter() relies on lockdep IRQ state, so switch that
+ * last -- this is very similar to the entry code.
+ */
+ trace_hardirqs_on_prepare();
+ lockdep_hardirqs_on_prepare(_THIS_IP_);
rcu_idle_enter();
+ lockdep_hardirqs_on(_THIS_IP_);
+
arch_cpu_idle();
+
+ /*
+ * OK, so IRQs are enabled here, but RCU needs them disabled to
+ * turn itself back on.. funny thing is that disabling IRQs
+ * will cause tracing, which needs RCU. Jump through hoops to
+ * make it 'work'.
+ */
+ raw_local_irq_disable();
+ lockdep_hardirqs_off(_THIS_IP_);
rcu_idle_exit();
+ lockdep_hardirqs_on(_THIS_IP_);
+ raw_local_irq_enable();
+
start_critical_timings();
trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
}