From: David Miller <davem@davemloft.net>
To: cmetcalf@tilera.com
Cc: xiyou.wangcong@gmail.com, cypher.w@gmail.com,
linux-kernel@vger.kernel.org, eric.dumazet@gmail.com,
netdev@vger.kernel.org
Subject: Re: IGMP and rwlock: Dead ocurred again on TILEPro
Date: Thu, 17 Feb 2011 15:11:47 -0800 (PST) [thread overview]
Message-ID: <20110217.151147.35033921.davem@davemloft.net> (raw)
In-Reply-To: <4D5DA96D.5060200@tilera.com>
From: Chris Metcalf <cmetcalf@tilera.com>
Date: Thu, 17 Feb 2011 18:04:13 -0500
> On 2/17/2011 5:53 PM, David Miller wrote:
>> From: Chris Metcalf <cmetcalf@tilera.com>
>> Date: Thu, 17 Feb 2011 17:49:46 -0500
>>
>>> The fix is to disable interrupts for the arch_read_lock family of methods.
>> How does that help handle the race when it happens between different
>> cpus, instead of between IRQ and non-IRQ context on the same CPU?
>
> There's no race in that case, since the lock code properly backs off and
> retries until the other cpu frees it. The distinction here is that the
> non-IRQ context is "wedged" by the IRQ context.
>
>> Why don't you just use the generic spinlock based rwlock code on Tile,
>> since that is all that your atomic instructions can handle
>> sufficiently?
>
> The tile-specific code encodes reader/writer information in the same 32-bit
> word that the test-and-set instruction manipulates, so it's more efficient
> both in space and time. This may not really matter for rwlocks, since no
> one cares much about them any more, but that was the motivation.
Ok, but IRQ disabling is going to be very expensive.
next prev parent reply other threads:[~2011-02-17 23:11 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-17 3:39 Fwd: IGMP and rwlock: Dead ocurred again on TILEPro Cypher Wu
2011-02-17 4:49 ` Américo Wang
2011-02-17 5:04 ` Cypher Wu
2011-02-17 5:42 ` Américo Wang
2011-02-17 5:46 ` David Miller
2011-02-17 6:39 ` Eric Dumazet
2011-02-17 22:49 ` Chris Metcalf
2011-02-17 22:53 ` David Miller
2011-02-17 23:04 ` Chris Metcalf
2011-02-17 23:11 ` David Miller [this message]
2011-02-17 23:18 ` Chris Metcalf
2011-02-18 3:16 ` Cypher Wu
2011-02-18 3:19 ` Cypher Wu
2011-02-18 7:08 ` Cypher Wu
2011-02-18 21:51 ` Chris Metcalf
2011-02-19 4:07 ` Cypher Wu
2011-02-20 13:33 ` Chris Metcalf
2011-03-01 18:30 ` [PATCH] arch/tile: fix deadlock bugs in rwlock implementation Chris Metcalf
2011-02-17 6:42 ` Fwd: IGMP and rwlock: Dead ocurred again on TILEPro Cypher Wu
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