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Re: [Qemu-devel] [PATCH 3/5] Migration thread mutex


From: Umesh Deshpande
Subject: Re: [Qemu-devel] [PATCH 3/5] Migration thread mutex
Date: Mon, 29 Aug 2011 09:49:45 -0400
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.20) Gecko/20110805 Thunderbird/3.1.12

On 08/29/2011 05:04 AM, Stefan Hajnoczi wrote:
On Sat, Aug 27, 2011 at 7:09 PM, Umesh Deshpande<address@hidden>  wrote:
This patch implements migrate_ram mutex, which protects the RAMBlock list
traversal in the migration thread during the transfer of a ram from their
addition/removal from the iothread.

Note: Combination of iothread mutex and migration thread mutex works as a
rw-lock. Both mutexes are acquired while modifying the ram_list members or RAM
block list.

Signed-off-by: Umesh Deshpande<address@hidden>
---
  arch_init.c   |   21 +++++++++++++++++++++
  cpu-all.h     |    3 +++
  exec.c        |   23 +++++++++++++++++++++++
  qemu-common.h |    2 ++
  4 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index 484b39d..9d02270 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -109,6 +109,7 @@ static int is_dup_page(uint8_t *page, uint8_t ch)

  static RAMBlock *last_block;
  static ram_addr_t last_offset;
+static uint64_t last_version;
[...]
  typedef struct RAMList {
+    QemuMutex mutex;    /* Protects RAM block list */
     uint8_t *phys_dirty;
+    uint32_t version;   /* To detect ram block addition/removal */
Is there a reason why RAMList.version is uint32_t but last_version is uint64_t?
No, my bad, they both should be consistent.




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