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Message-ID: <20140917093004.GB1213@gondor.apana.org.au> Date: Wed, 17 Sep 2014 17:30:04 +0800 From: Herbert Xu <herbert@...dor.apana.org.au> To: Amos Kong <akong@...hat.com> Cc: virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org, m@...s.ch, mb@...sch.de, mpm@...enic.com, rusty@...tcorp.com.au, amit.shah@...hat.com, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2 0/3] fix stuck in accessing hwrng attributes On Tue, Sep 16, 2014 at 12:02:26AM +0800, Amos Kong wrote: > If we read hwrng by long-running dd process, it takes too much cpu > time and almost hold the mutex lock. When we check hwrng attributes > from sysfs by cat, it gets stuck in waiting the lock releaseing. > The problem can only be reproduced with non-smp guest with slow backend. > > This patchset resolves the issue by changing rng_dev_read() to always > schedule 10 jiffies after release mutex lock, then cat process can > have chance to get the lock and execute protected code without stuck. Sorry I'm not going to accept your fix which simply papers over the problem. Please bite the bullet and convert this over to RCU. Cheers, -- Email: Herbert Xu <herbert@...dor.apana.org.au> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- 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/
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