From: Rémi Bernon rbernon@codeweavers.com
The client should check that the lower SEQUENCE_MASK_BITS are zero before reading the data and confirm that the number is unchanged when it's finished.
Based on a patch by Huw Davies huw@codeweavers.com. --- server/protocol.def | 1 + server/queue.c | 22 ++++++++++++++++------ 2 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/server/protocol.def b/server/protocol.def index 1f56b8f0bf7..a82ffe90e5e 100644 --- a/server/protocol.def +++ b/server/protocol.def @@ -902,6 +902,7 @@ struct shared_cursor
struct desktop_shared_memory { + unsigned int seq; /* sequence number - server updating if (seq & 1) != 0 */ struct shared_cursor cursor; /* global cursor information */ }; typedef volatile struct desktop_shared_memory desktop_shm_t; diff --git a/server/queue.c b/server/queue.c index 7ee96c9325e..8f7c74724e8 100644 --- a/server/queue.c +++ b/server/queue.c @@ -232,14 +232,24 @@ static unsigned int last_input_time; static cursor_pos_t cursor_history[64]; static unsigned int cursor_history_latest;
-#define SHARED_WRITE_BEGIN( object, type ) \ - do { \ - const type *__shared = (object)->shared; \ - type *shared = (type *)__shared; \ +#if defined(__i386__) || defined(__x86_64__) +#define __SHARED_INCREMENT_SEQ( x ) ++(x) +#else +#define __SHARED_INCREMENT_SEQ( x ) __atomic_add_fetch( &(x), 1, __ATOMIC_RELEASE ) +#endif + +#define SHARED_WRITE_BEGIN( object, type ) \ + do { \ + const type *__shared = (object)->shared; \ + type *shared = (type *)__shared; \ + unsigned int __seq = __SHARED_INCREMENT_SEQ( shared->seq ); \ + assert( (__seq & 1) != 0 ); \ do
-#define SHARED_WRITE_END \ - while(0); \ +#define SHARED_WRITE_END \ + while(0); \ + __seq = __SHARED_INCREMENT_SEQ( shared->seq ) - __seq; \ + assert( __seq == 1 ); \ } while(0)
static void queue_hardware_message( struct desktop *desktop, struct message *msg, int always_queue );