linux-kernel - Re: [PATCH] lockdep: Fix wait context check on softirq for PREEMPT

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Message-ID: <Z2W-veam4RP1C6zM@boqun-archlinux>
Date: Fri, 20 Dec 2024 11:00:13 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: Ryo Takakura <ryotkkr98@...il.com>
Cc: bigeasy@...utronix.de, clrkwllms@...nel.org,
	linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev,
	longman@...hat.com, mingo@...hat.com, peterz@...radead.org,
	rostedt@...dmis.org, tglx@...utronix.de, will@...nel.org
Subject: Re: [PATCH] lockdep: Fix wait context check on softirq for PREEMPT_RT

On Sat, Dec 21, 2024 at 01:10:16AM +0900, Ryo Takakura wrote:
> 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.

Good! Do you want to continue working on this based on the above
changes? If so, feel free.

Regards,
Boqun

> 
> Sincerely,
> Ryo Takakura