linux-kernel - Re: [patch] cpufreq: mark cpufreq_tsc() as core_initcall

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: <20061127165649.GB279@oleg>
Date:	Mon, 27 Nov 2006 19:56:49 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	"Paul E. McKenney" <paulmck@...ibm.com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Jens Axboe <jens.axboe@...cle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] cpufreq: mark cpufreq_tsc() as core_initcall_sync

On 11/27, Oleg Nesterov wrote:
>
> so synchronize_xxx() should be
> 
> 	void synchronize_xxx(struct xxx_struct *sp)
> 	{
> 		int idx;
> 
> 		smp_mb();
> 		mutex_lock(&sp->mutex);
> 
> 		idx = sp->completed & 0x1;
> 		if (atomic_read(sp->ctr + idx) == 1)
> 			goto out;
> 
> 		atomic_inc(sp->ctr + (idx ^ 0x1));
> 		sp->completed++;
> 
> 		atomic_dec(sp->ctr + idx);
> 		wait_event(sp->wq, !atomic_read(sp->ctr + idx));
> 	out:
> 		mutex_unlock(&sp->mutex);
> 	}
> 
> Yes, Alan was right, spinlock_t makes the code simpler.

Damn, it needs another mb() at the end,

	void synchronize_xxx(struct xxx_struct *sp)
	{
		int idx;

		smp_mb();
		mutex_lock(&sp->mutex);

		idx = sp->completed & 0x1;
		if (atomic_read(sp->ctr + idx) == 1)
			goto out;

		atomic_inc(sp->ctr + (idx ^ 0x1));
		sp->completed++;

		atomic_dec(sp->ctr + idx);
		wait_event(sp->wq, !atomic_read(sp->ctr + idx));
	out:
		mutex_unlock(&sp->mutex);
		smp_mb();
	}

Oleg.

-
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/