From: Paolo Bonzini <pbonzini@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Umesh Deshpande <udeshpan@redhat.com>,
qemu-devel@nongnu.org, kvm@vger.kernel.org, quintela@redhat.com
Subject: Re: [Qemu-devel] [RFC PATCH v4 2/5] ramlist mutex
Date: Tue, 23 Aug 2011 13:41:48 +0200 [thread overview]
Message-ID: <4E5391FC.1060703@redhat.com> (raw)
In-Reply-To: <20110823091726.GA5797@amt.cnet>
On 08/23/2011 11:17 AM, Marcelo Tosatti wrote:
>>> > > typedef struct RAMList {
>>> > > + QemuMutex mutex;
>>> > > uint8_t *phys_dirty;
>>> > > QLIST_HEAD(ram, RAMBlock) blocks;
>>> > > QLIST_HEAD(, RAMBlock) blocks_mru;
>> >
>> > A comment on what the mutex protects would be good.
Indeed, especially because Umesh wanted to use the ramlist+iothread
combo as a rw-lock: iothread = read-lock for the I/O thread, ramlist =
read-lock for the migration thread, together = exclusive (write) lock.
But I think I talked him out of this. :) It's not a bad idea in
general, it just sounds like overkill in this case.
> And on the lock ordering.
I think when only two locks are involved, we can always assume iothread
is outer and the other is inner. Do you agree?
Paolo
next prev parent reply other threads:[~2011-08-23 11:41 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-17 3:56 [Qemu-devel] [RFC PATCH v4 0/5] Separate thread for VM migration Umesh Deshpande
2011-08-17 3:56 ` [Qemu-devel] [RFC PATCH v4 1/5] MRU ram list Umesh Deshpande
2011-08-17 3:56 ` [Qemu-devel] [RFC PATCH v4 2/5] ramlist mutex Umesh Deshpande
2011-08-17 6:28 ` Paolo Bonzini
2011-08-19 6:20 ` Umesh Deshpande
2011-08-22 6:48 ` Paolo Bonzini
2011-08-23 9:15 ` Marcelo Tosatti
2011-08-23 9:17 ` Marcelo Tosatti
2011-08-23 11:41 ` Paolo Bonzini [this message]
2011-08-23 12:16 ` Marcelo Tosatti
2011-08-17 3:56 ` [Qemu-devel] [RFC PATCH v4 3/5] separate migration bitmap Umesh Deshpande
2011-08-17 3:56 ` [Qemu-devel] [RFC PATCH v4 4/5] separate thread for VM migration Umesh Deshpande
2011-08-17 7:13 ` Paolo Bonzini
2011-08-17 3:56 ` [Qemu-devel] [RFC PATCH v3 5/5] Making iothread block for migrate_cancel Umesh Deshpande
2011-08-17 7:14 ` Paolo Bonzini
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