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Date: Wed, 21 May 2014 08:48:24 +0800 From: Chen Yucong <slaoub@...il.com> To: Borislav Petkov <bp@...en8.de> Cc: tony.luck@...el.com, ak@...ux.intel.com, ying.huang@...el.com, seto.hidetoshi@...fujitsu.com, linux-kernel@...r.kernel.org, linux-edac@...r.kernel.org Subject: Re: [PATCH v2] x86/mce: Distirbute the clear operation of mces_seen to Per-CPU rather than only monarch CPU On Tue, 2014-05-20 at 19:33 +0200, Borislav Petkov wrote: > On Tue, May 20, 2014 at 10:11:25AM +0800, Chen Yucong wrote: > > mces_seen is a Per-CPU variable which should only be accessed by > > Per-CPU as possible. So the clear operation of mces_seen should also > > be lcoal to Per-CPU rather than monarch CPU. > > > > Meanwhile, there is also a potential risk that mces_seen will not > > be be cleared if a timeout occors in mce_end for monarch CPU. As a > > reuslt, the stale value of mces_seen will reappear on the next mce. > > I don't know how many times I have to tell you this already: if we reach > the timeout, we have a much bigger friggin' problem! Even if we do not take into account timeout, we should distribute the clear operation of mces_seen to Per-CPU rather then monarch CPU. mce_regin, which is only called by monarch CPU, can be used for system panics as quickly as possible if there is a truly data corrupting error. But Monarch CPU don't have to help all other CPU to clean mces_clean. One advantage of Per-CPU is the isolation of errors propagation, being so, why do not we clean mces_seen by Per-CPU? You say, "you need to do the cleaning in mce_reign because the monarch cpu has to run last after all other cpus have scanned their mce banks." But this is not an adequate explanation. thx! cyc > > What you could do instead is make the machine panic in the tolerant==1, > i.e., the default case, in mce_timed_out(). > > Basically, in the case any core is stuck and we reach a timeout, we want > to panic the whole box immediately. There's a very little chance we can > recover so panic is the only sane thing left to do. > > Ok? > -- 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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