Re: [PATCH] lockdep: Fix wait context check on softirq for PREEMPT_RT

[Ryo Takakura]

On Thu, 19 Dec 2024 14:27:11 -0800, Boqun Feng wrote:
>The following is the rough idea:
>
>Regards,
>Boqun
>
>----->8
>diff --git a/include/linux/bottom_half.h b/include/linux/bottom_half.h
>index fc53e0ad56d9..7191a753e983 100644
>--- a/include/linux/bottom_half.h
>+++ b/include/linux/bottom_half.h
>@@ -4,6 +4,7 @@
> 
> #include <linux/instruction_pointer.h>
> #include <linux/preempt.h>
>+#include <linux/lockdep.h>
> 
> #if defined(CONFIG_PREEMPT_RT) || defined(CONFIG_TRACE_IRQFLAGS)
> extern void __local_bh_disable_ip(unsigned long ip, unsigned int cnt);
>@@ -15,9 +16,12 @@ static __always_inline void __local_bh_disable_ip(unsigned long ip, unsigned int
> }
> #endif
> 
>+extern struct lockdep_map bh_lock_map;
>+
> static inline void local_bh_disable(void)
> {
> 	__local_bh_disable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET);
>+	lock_map_acquire_read(&bh_lock_map);
> }
> 
> extern void _local_bh_enable(void);
>@@ -25,11 +29,13 @@ extern void __local_bh_enable_ip(unsigned long ip, unsigned int cnt);
> 
> static inline void local_bh_enable_ip(unsigned long ip)
> {
>+	lock_map_release(&bh_lock_map);
> 	__local_bh_enable_ip(ip, SOFTIRQ_DISABLE_OFFSET);
> }
> 
> static inline void local_bh_enable(void)
> {
>+	lock_map_release(&bh_lock_map);
> 	__local_bh_enable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET);
> }
> 
>diff --git a/kernel/softirq.c b/kernel/softirq.c
>index 8b41bd13cc3d..17d9bf6e0caf 100644
>--- a/kernel/softirq.c
>+++ b/kernel/softirq.c
>@@ -1066,3 +1066,13 @@ unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
> {
> 	return from;
> }
>+
>+static struct lock_class_key bh_lock_key;
>+struct lockdep_map bh_lock_map = {
>+	.name = "local_bh",
>+	.key = &bh_lock_key,
>+	.wait_type_outer = LD_WAIT_FREE,
>+	.wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_RT makes BH preemptible. */
>+	.lock_type = LD_LOCK_PERCPU,
>+};
>+EXPORT_SYMBOL_GPL(bh_lock_map);

Self-tests are now all passing. Thanks!
It looks good to me.

Sincerely,
Ryo Takakura