On Tue, Aug 23, 2011 at 11:12:48PM -0400, Umesh Deshpande wrote:
> ramlist mutex is implemented to protect the RAMBlock list traversal in the
> migration thread 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 <udeshpan@xxxxxxxxxx>
> ---
> 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;
>
> static int ram_save_block(QEMUFile *f)
> {
> @@ -170,6 +171,7 @@ static int ram_save_block(QEMUFile *f)
>
> last_block = block;
> last_offset = offset;
> + last_version = ram_list.version;
>
> return bytes_sent;
> }
> @@ -270,6 +272,7 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
> bytes_transferred = 0;
> last_block = NULL;
> last_offset = 0;
> + last_version = ram_list.version = 0;
> sort_ram_list();
>
> /* Make sure all dirty bits are set */
> @@ -298,6 +301,17 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
> bytes_transferred_last = bytes_transferred;
> bwidth = qemu_get_clock_ns(rt_clock);
>
> + if (stage != 3) {
> + qemu_mutex_lock_migthread();
> + qemu_mutex_unlock_iothread();
> + }
> +
> + if (ram_list.version != last_version) {
> + /* RAM block added or removed */
> + last_block = NULL;
> + last_offset = 0;
> + }
> +
> while (!qemu_file_rate_limit(f)) {
> int bytes_sent;
>
> @@ -308,6 +322,13 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
> }
> }
>
> + if (stage != 3) {
> + qemu_mutex_unlock_migthread();
> + qemu_mutex_lock_iothread();
> + /* Lock ordering : iothread mutex is always acquired outside migthread
> + * mutex critical section to avoid deadlock */
> + }
> +
> bwidth = qemu_get_clock_ns(rt_clock) - bwidth;
> bwidth = (bytes_transferred - bytes_transferred_last) / bwidth;
>
> diff --git a/cpu-all.h b/cpu-all.h
> index 6b217a2..b85483f 100644
> --- a/cpu-all.h
> +++ b/cpu-all.h
> @@ -21,6 +21,7 @@
>
> #include "qemu-common.h"
> #include "cpu-common.h"
> +#include "qemu-thread.h"
>
> /* some important defines:
> *
> @@ -932,7 +933,9 @@ typedef struct RAMBlock {
> } RAMBlock;
>
> typedef struct RAMList {
> + QemuMutex mutex; /* Protects RAM block list */
> uint8_t *phys_dirty;
> + uint32_t version; /* To detect ram block addition/removal */
> QLIST_HEAD(ram, RAMBlock) blocks;
> QLIST_HEAD(, RAMBlock) blocks_mru;
> } RAMList;
> diff --git a/exec.c b/exec.c
> index c5c247c..7627483 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -582,6 +582,7 @@ void cpu_exec_init_all(unsigned long tb_size)
> code_gen_alloc(tb_size);
> code_gen_ptr = code_gen_buffer;
> page_init();
> + qemu_mutex_init(&ram_list.mutex);
> #if !defined(CONFIG_USER_ONLY)
> io_mem_init();
> #endif
> @@ -2802,6 +2803,16 @@ static long gethugepagesize(const char *path)
> return fs.f_bsize;
> }
>
> +void qemu_mutex_lock_migthread(void)
> +{
> + qemu_mutex_lock(&ram_list.mutex);
> +}
qemu_mutex_lock_ramlist is a better name, _migthread is confusing.
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
