linux-kernel - Re: [PATCH v2] powerpc ticket locks

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]

Date:	Tue, 11 Feb 2014 15:09:23 +0530
From:	Raghavendra KT <raghavendra.kt.linux@...il.com>
To:	Torsten Duwe <duwe@....de>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Anton Blanchard <anton@...ba.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Scott Wood <scottwood@...escale.com>,
	Tom Musta <tommusta@...il.com>, Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linuxppc-dev@...ts.ozlabs.org,
	Raghavendra KT <raghavendra.kt@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2] powerpc ticket locks

On Fri, Feb 7, 2014 at 10:28 PM, Torsten Duwe <duwe@....de> wrote:
> Ticket locks for ppc, version 2. Changes since v1:
> * The atomically exchanged entity is always 32 bits.
> * asm inline string variations thus removed.
> * Carry the additional holder hint only #if defined(CONFIG_PPC_SPLPAR)
>
> Signed-off-by: Torsten Duwe <duwe@...e.de>
> --
[...]
> +static __always_inline void arch_spin_lock(arch_spinlock_t *lock)
>  {
> +       register struct __raw_tickets old, tmp,
> +               inc = { .tail = TICKET_LOCK_INC };
> +
>         CLEAR_IO_SYNC;
> -       while (1) {
> -               if (likely(__arch_spin_trylock(lock) == 0))
> -                       break;
> +       __asm__ __volatile__(
> +"1:    lwarx   %0,0,%4         # arch_spin_lock\n"
> +"      add     %1,%3,%0\n"
> +       PPC405_ERR77(0, "%4")
> +"      stwcx.  %1,0,%4\n"
> +"      bne-    1b"
> +       : "=&r" (old), "=&r" (tmp), "+m" (lock->tickets)
> +       : "r" (inc), "r" (&lock->tickets)
> +       : "cc");
> +
> +       if (likely(old.head == old.tail))
> +               goto out;
> +
> +       for (;;) {
> +               unsigned count = 100;

I am sure you wanted to tune the total loops to typical lock holding time ...
--
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/