On Thu, Sep 17, 2020 at 01:16:46PM -0400, Steven Rostedt wrote:
> Hi Peter,
>
> I ran my tests on a series of patches on top of 5.9-rc4, and hit the
> following splat:
>
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 2557 at kernel/rcu/tree.c:1058 rcu_irq_enter+0x15/0x20
> RIP: 0010:rcu_irq_enter+0x15/0x20
> Call Trace:
> rcu_irq_enter_irqson+0x21/0x40
> trace_preempt_off+0x6e/0xd0
> unwind_next_frame+0x41/0x560
> __unwind_start+0x153/0x1e0
> arch_stack_walk+0x76/0x100
> stack_trace_save+0x4b/0x70
> save_trace+0x42/0x350
> __lock_acquire+0x1858/0x2460
> lock_acquire+0xdc/0x3b0
> cpuset_read_lock+0x26/0xc0
> What looks to have happened was:
>
> cpuset_read_lock()
> lockdep called
> save stack trace
> preempt_disable()
> trace_preempt_disable();
> rcu_irq_enter_irqson();
> local_irq_save() (ignored by lockdep due to recursion set)
> rcu_irq_enter();
> lockdep_assert_irqs_disabled() (no, because it was
> ignored by recursion being set)
>
> BOOM!
>
>
> Thoughts?
> diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
> index 6a584b3e5c74..3e5bc1dd71c6 100644
> --- a/include/linux/lockdep.h
> +++ b/include/linux/lockdep.h
> @@ -550,7 +550,8 @@ do {
> \
>
> #define lockdep_assert_irqs_disabled()
> \
> do { \
> - WARN_ON_ONCE(debug_locks && raw_cpu_read(hardirqs_enabled)); \
> + WARN_ON_ONCE(debug_locks && raw_cpu_read(hardirqs_enabled) && \
> + likely(!(current->lockdep_recursion & LOCKDEP_RECURSION_MASK)));\
> } while (0)
Blergh, IIRC there's header hell that way. The sane fix is killing off
that trace_*_rcuidle() disease.
But I think this will also cure it.
---
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 6a339ce328e0..4f90293d170b 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -432,7 +432,7 @@ bool unwind_next_frame(struct unwind_state *state)
return false;
/* Don't let modules unload while we're reading their ORC data. */
- preempt_disable();
+ preempt_disable_notrace();
/* End-of-stack check for user tasks: */
if (state->regs && user_mode(state->regs))
@@ -612,14 +612,14 @@ bool unwind_next_frame(struct unwind_state *state)
goto err;
}
- preempt_enable();
+ preempt_enable_notrace();
return true;
err:
state->error = true;
the_end:
- preempt_enable();
+ preempt_enable_notrace();
state->stack_info.type = STACK_TYPE_UNKNOWN;
return false;
}
