From: "Xu, Quan" <quan.xu@intel.com>
To: Dario Faggioli <dario.faggioli@citrix.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
Jan Beulich <JBeulich@suse.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: [PATCH v2 1/2] IOMMU/spinlock: Fix a bug found in AMD IOMMU initialization.
Date: Thu, 10 Mar 2016 05:36:01 +0000 [thread overview]
Message-ID: <945CA011AD5F084CBEA3E851C0AB28894B85FA82@SHSMSX101.ccr.corp.intel.com> (raw)
In-Reply-To: <1457534700.3102.387.camel@citrix.com>
On March 09, 2016 10:45pm, Dario Faggioli wrote:
> On Wed, 2016-03-09 at 06:55 -0700, Jan Beulich wrote:
> > >
> > > > > On 09.03.16 at 14:46, <quan.xu@intel.com> wrote:
> > > Now I am still not clear for this point- "this inconsistency might
> > > lead to deadlock".
> > > I think it is similar to 'mixing interrupt disabled and enabled
> > > spinlocks is something we disallow'.
> > > I hope you can give me an example about how to lead to deadlock.
> > The implication from disabling interrupts while acquiring a lock is
> > that the lock is also being acquired by some interrupt handler. If you
> > mix acquire types, the one not disabling interrupts is prone to be
> > interrupted, and the interrupt trying to get hold of the lock the same
> > CPU already owns.
> >
> Exactly.
>
> There are a few other nice writeup online as well.
>
> The most famous one, I guess, is this one from Linus (look at "Lesson
> 3: spinlocks revisited.")
> https://www.kernel.org/doc/Documentation/locking/spinlocks.txt
>
> And, of course, there's the comment inside check_lock(), in
> xen/common/spinlock.c, in Xen's codebase, where another example of how it
> could be dangerous to mix, even if multiple cpus are involved.
>
Dario, thanks! You know, it helped me a lot.
Quan
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next prev parent reply other threads:[~2016-03-10 5:36 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-09 3:08 [PATCH v2 0/2] Make the pcidevs_lock a recursive one Quan Xu
2016-03-09 3:08 ` [PATCH v2 1/2] IOMMU/spinlock: Fix a bug found in AMD IOMMU initialization Quan Xu
2016-03-09 5:19 ` Tian, Kevin
2016-03-09 7:31 ` Xu, Quan
2016-03-09 10:09 ` Jan Beulich
2016-03-09 10:24 ` Dario Faggioli
2016-03-09 12:52 ` Xu, Quan
2016-03-09 13:19 ` Dario Faggioli
2016-03-09 13:46 ` Xu, Quan
2016-03-09 13:55 ` Jan Beulich
2016-03-09 14:45 ` Dario Faggioli
2016-03-10 5:36 ` Xu, Quan [this message]
2016-03-10 3:21 ` Xu, Quan
2016-03-09 3:08 ` [PATCH v2 2/2] IOMMU/spinlock: Make the pcidevs_lock a recursive one Quan Xu
2016-03-09 5:21 ` Tian, Kevin
2016-03-09 5:50 ` Xu, Quan
2016-03-09 12:18 [PATCH v2 1/2] IOMMU/spinlock: Fix a bug found in AMD IOMMU initialization Xu, Quan
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