linux-kernel - Re: [PATCH] lglock: Use spinlock_t instead of arch_spinlock

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20150326160325.GA21418@twins.programming.kicks-ass.net>
Date:	Thu, 26 Mar 2015 17:03:25 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Daniel Wagner <daniel.wagner@...-carit.de>
Cc:	Jeff Layton <jlayton@...chiereds.net>,
	Ingo Molnar <mingo@...hat.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andi Kleen <andi@...stfloor.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lglock: Use spinlock_t instead of arch_spinlock_t

On Thu, Mar 26, 2015 at 04:02:08PM +0100, Daniel Wagner wrote:
> @@ -67,9 +67,9 @@ void lg_global_lock(struct lglock *lg)
>  	preempt_disable();
>  	lock_acquire_exclusive(&lg->lock_dep_map, 0, 0, NULL, _RET_IP_);
>  	for_each_possible_cpu(i) {
> -		arch_spinlock_t *lock;
> +		spinlock_t *lock;
>  		lock = per_cpu_ptr(lg->lock, i);
> -		arch_spin_lock(lock);
> +		spin_lock(lock);
>  	}
>  }

Nope, that'll blow up in two separate places.

One: lockdep, it can only track a limited number of held locks, and it
will further report a recursion warning on the 2nd cpu.

Second: preempt_count_add(), spin_lock() does preempt_disable(), with
enough CPUs you'll overflow the preempt counter (255).


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/