linux-kernel - Re: [PATCH] lockdep: Do no validate wait context for novalidate class

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Message-ID: <20200820090511.umk4x7xmdylnxcen@linutronix.de>
Date:   Thu, 20 Aug 2020 11:05:11 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        tglx@...utronix.de
Subject: Re: [PATCH] lockdep: Do no validate wait context for novalidate class

On 2020-06-29 22:15:29 [+0200], To linux-kernel@...r.kernel.org wrote:
> The novalidate class is ignored in the lockchain validation but is
> considered in the wait context validation.
> If a mutex and a spinlock_t is ignored by using
> lockdep_set_novalidate_class() then both locks will share the same lock
> class. From the wait validation point of view the mutex will then appear
> like a spinlock_t and the validator will complain if another mutex will
> be acquired.
> 
> Ignore the nonvalidate locks from wait context checking.

ping :)

> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
>  kernel/locking/lockdep.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 29a8de4c50b90..fb9a642d8ebef 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -4067,7 +4067,7 @@ static int check_wait_context(struct task_struct *curr, struct held_lock *next)
>  	 */
>  	for (depth = curr->lockdep_depth - 1; depth >= 0; depth--) {
>  		struct held_lock *prev = curr->held_locks + depth;
> -		if (prev->irq_context != next->irq_context)
> +		if (prev->check && prev->irq_context != next->irq_context)
>  			break;
>  	}
>  	depth++;
> @@ -4078,6 +4078,9 @@ static int check_wait_context(struct task_struct *curr, struct held_lock *next)
>  		struct held_lock *prev = curr->held_locks + depth;
>  		short prev_inner = hlock_class(prev)->wait_type_inner;
>  
> +		if (!prev->check)
> +			continue;
> +
>  		if (prev_inner) {
>  			/*
>  			 * We can have a bigger inner than a previous one

Sebastian