On Wed, Jun 03, 2020 at 04:44:17PM -0700, Guenter Roeck wrote:
>
> sparc32 smp images in next-20200603 still crash for me with a spinlock
> recursion. s390 images hang early in boot. Several others (alpha, arm64,
> various ppc) don't even compile. I can run some more bisects over time,
> but this is becoming a full-time job :-(.
I've been able to bisect s390 hang to commit b614345f52bc ("x86/entry:
Clarify irq_{enter,exit}_rcu()").
After this commit, lockdep_hardirq_exit() is called twice on s390 (and
others) - one time in irq_exit_rcu() and another one in irq_exit():
/**
* irq_exit_rcu() - Exit an interrupt context without updating RCU
*
* Also processes softirqs if needed and possible.
*/
void irq_exit_rcu(void)
{
__irq_exit_rcu();
/* must be last! */
lockdep_hardirq_exit();
}
/**
* irq_exit - Exit an interrupt context, update RCU and lockdep
*
* Also processes softirqs if needed and possible.
*/
void irq_exit(void)
{
irq_exit_rcu();
rcu_irq_exit();
/* must be last! */
lockdep_hardirq_exit();
}
Removing the call in irq_exit() make s390 boot again, and judgung by the
x86 entry code, the comment /* must be last! */ is stale...
@Peter, @Thomas, can you comment please?
>From e51d50ee6f4d1f446decf91c2c67230da14ff82c Mon Sep 17 00:00:00 2001
From: Mike Rapoport <r...@linux.ibm.com>
Date: Thu, 4 Jun 2020 12:37:03 +0300
Subject: [PATCH] softirq: don't call lockdep_hardirq_exit() twice
After commit b614345f52bc ("x86/entry: Clarify irq_{enter,exit}_rcu()")
lockdep_hardirq_exit() is called twice on every architecture that uses
irq_exit(): one time in irq_exit_rcu() and another one in irq_exit().
Remove the extra call in irq_exit().
Signed-off-by: Mike Rapoport <r...@linux.ibm.com>
---
kernel/softirq.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/kernel/softirq.c b/kernel/softirq.c
index a3eb6eba8c41..7523f4ce4c1d 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -427,7 +427,6 @@ static inline void __irq_exit_rcu(void)
void irq_exit_rcu(void)
{
__irq_exit_rcu();
- /* must be last! */
lockdep_hardirq_exit();
}
@@ -440,8 +439,6 @@ void irq_exit(void)
{
irq_exit_rcu();
rcu_irq_exit();
- /* must be last! */
- lockdep_hardirq_exit();
}
/*
--
2.26.2
> Guenter
--
Sincerely yours,
Mike.
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