From: Paolo Bonzini <pbonzini@redhat.com>
To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Peter Maydell <peter.maydell@linaro.org>,
Anthony Liguori <aliguori@us.ibm.com>,
Jan Kiszka <jan.kiszka@siemens.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
liu ping fan <qemulist@gmail.com>,
qemu-devel@nongnu.org,
Vasilis Liaskovitis <vasilis.liaskovitis@profitbricks.com>
Subject: Re: [Qemu-devel] [PATCH 2/5] hostmem: make hostmem global and RAM hotunplg safe
Date: Fri, 12 Apr 2013 12:03:40 +0200 [thread overview]
Message-ID: <5167DBFC.2060405@redhat.com> (raw)
In-Reply-To: <20130412083855.GC31055@stefanha-thinkpad.redhat.com>
Il 12/04/2013 10:38, Stefan Hajnoczi ha scritto:
>> > Yes, protect. Supposed we have HostMem A, and it will become B. Then
>> > hostmem_lookup will either see A or B. If it see A, it should use A
>> > refcnt agaist hostmem_listener_commit to drop A. This refcnt has no
>> > relation with mr's object's refcnt.
> My question is why you are accessing cur_hostmem outside hostmem_lock
> but then assigning it inside the lock on the next line...
>
>>>> > >> + cur_hostmem = next_hostmem;
> ...here.
>
> If you want an atomic exchange then tmp = cur_hostmem should be inside
> the lock.
It will work because readers will grab either the hostmem_lock or the
BQL, while writers will grab both. A kind of local/global lock, but I'm
not sure it was intentional. :) It's simpler to just move the read
inside the lock.
Paolo
next prev parent reply other threads:[~2013-04-12 10:03 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-01 8:20 [Qemu-devel] [PATCH 0/5] proposal to make hostmem listener RAM unplug safe Liu Ping Fan
2013-04-01 8:20 ` [Qemu-devel] [PATCH 1/5] memory: add ref/unref interface for MemroyRegionOps Liu Ping Fan
2013-04-11 9:49 ` Stefan Hajnoczi
2013-04-12 4:12 ` liu ping fan
2013-04-01 8:20 ` [Qemu-devel] [PATCH 2/5] hostmem: make hostmem global and RAM hotunplg safe Liu Ping Fan
2013-04-02 6:11 ` li guang
2013-04-11 10:09 ` Paolo Bonzini
2013-04-12 6:46 ` liu ping fan
2013-04-12 8:21 ` Stefan Hajnoczi
2013-04-11 10:11 ` Stefan Hajnoczi
2013-04-11 10:26 ` Paolo Bonzini
2013-04-12 3:55 ` liu ping fan
2013-04-12 8:38 ` Stefan Hajnoczi
2013-04-12 10:03 ` Paolo Bonzini [this message]
2013-04-15 1:42 ` liu ping fan
2013-04-15 6:38 ` Paolo Bonzini
2013-04-01 8:20 ` [Qemu-devel] [PATCH 3/5] vring: use hostmem's RAM safe api Liu Ping Fan
2013-04-11 10:15 ` Stefan Hajnoczi
2013-04-12 4:49 ` liu ping fan
2013-04-12 8:41 ` Stefan Hajnoczi
2013-04-01 8:20 ` [Qemu-devel] [PATCH 4/5] virtio-blk: release reference to RAM's memoryRegion Liu Ping Fan
2013-04-02 5:58 ` li guang
2013-04-12 4:44 ` liu ping fan
2013-04-11 10:20 ` Stefan Hajnoczi
2013-04-12 4:48 ` liu ping fan
2013-04-12 8:45 ` Stefan Hajnoczi
2013-04-12 9:05 ` liu ping fan
2013-04-16 7:57 ` Stefan Hajnoczi
2013-04-16 8:12 ` Paolo Bonzini
2013-04-01 8:20 ` [Qemu-devel] [PATCH 5/5] hostmem: init/finalize hostmem listener Liu Ping Fan
2013-04-11 10:02 ` Paolo Bonzini
2013-04-11 12:08 ` liu ping fan
2013-04-11 13:14 ` Paolo Bonzini
2013-06-13 4:38 ` [Qemu-devel] about atexit() (was: [PATCH 5/5] hostmem: init/finalize hostmem listener) Amos Kong
2013-06-13 8:51 ` liu ping fan
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