From 0fe08538e9b54abc95ccad708890523b2e284340 Mon Sep 17 00:00:00 2001
From: Cedric Roux <cedric.roux@eurecom.fr>
Date: Mon, 21 Mar 2016 16:44:12 +0100
Subject: [PATCH] add __synch_synchronize for the T_cache it probably makes
things zillion times slower but it seems to be necessary
---
T.c | 13 ++++++++++---
T.h | 6 ++++--
tracer/main.c | 10 +++++++++-
3 files changed, 23 insertions(+), 6 deletions(-)
diff --git a/T.c b/T.c
index a33d1e90b6..13bf25b324 100644
--- a/T.c
+++ b/T.c
@@ -54,9 +54,16 @@ static void *T_send_thread(void *_)
{
while (1) {
usleep(5000);
+ __sync_synchronize();
while (T_cache[T_busylist_head].busy) {
- char *b = T_cache[T_busylist_head].buffer;
- int l = T_cache[T_busylist_head].length;
+ char *b;
+ int l;
+ /* TODO: be sure about those memory barriers - in doubt one is
+ * put here too
+ */
+ __sync_synchronize();
+ b = T_cache[T_busylist_head].buffer;
+ l = T_cache[T_busylist_head].length;
while (l) {
int done = write(T_socket, b, l);
if (done <= 0) {
@@ -123,7 +130,7 @@ void T_connect_to_tracer(char *addr, int port)
#ifdef T_USE_SHARED_MEMORY
/* setup shared memory */
- T_shm_fd = shm_open(T_SHM_FILENAME, O_RDWR, 0666);
+ T_shm_fd = shm_open(T_SHM_FILENAME, O_RDWR /*| O_SYNC*/, 0666);
shm_unlink(T_SHM_FILENAME);
if (T_shm_fd == -1) { perror(T_SHM_FILENAME); abort(); }
T_cache = mmap(NULL, T_CACHE_SIZE * sizeof(T_cache_t),
diff --git a/T.h b/T.h
index 405594f2d4..6797213d31 100644
--- a/T.h
+++ b/T.h
@@ -118,16 +118,18 @@ extern T_cache_t *T_cache;
#ifdef T_USE_SHARED_MEMORY
#define T_SEND() \
- T_cache[T_LOCAL_slot].busy = 1; \
T_cache[T_LOCAL_slot].length = T_LOCAL_size; \
+ __sync_synchronize(); \
+ T_cache[T_LOCAL_slot].busy = 1; \
T_send(T_LOCAL_buf, T_LOCAL_size)
#else /* T_USE_SHARED_MEMORY */
/* when not using shared memory, wait for send to finish */
#define T_SEND() \
- T_cache[T_LOCAL_slot].busy = 1; \
T_cache[T_LOCAL_slot].length = T_LOCAL_size; \
+ __sync_synchronize(); \
+ T_cache[T_LOCAL_slot].busy = 1; \
T_send(T_LOCAL_buf, T_LOCAL_size); \
while (T_cache[T_LOCAL_slot].busy) usleep(1*1000)
diff --git a/tracer/main.c b/tracer/main.c
index 18ed8087cc..cf8f8aac85 100644
--- a/tracer/main.c
+++ b/tracer/main.c
@@ -356,7 +356,8 @@ void wait_message(void)
void init_shm(void)
{
- int s = shm_open(T_SHM_FILENAME, O_RDWR | O_CREAT, 0666);
+ int i;
+ int s = shm_open(T_SHM_FILENAME, O_RDWR | O_CREAT /*| O_SYNC*/, 0666);
if (s == -1) { perror(T_SHM_FILENAME); abort(); }
if (ftruncate(s, T_CACHE_SIZE * sizeof(T_cache_t)))
{ perror(T_SHM_FILENAME); abort(); }
@@ -365,6 +366,12 @@ void init_shm(void)
if (T_cache == NULL)
{ perror(T_SHM_FILENAME); abort(); }
close(s);
+
+ /* let's garbage the memory to catch some potential problems
+ * (think multiprocessor sync issues, barriers, etc.)
+ */
+ memset(T_cache, 0x55, T_CACHE_SIZE * sizeof(T_cache_t));
+ for (i = 0; i < T_CACHE_SIZE; i++) T_cache[i].busy = 0;
}
#endif /* T_USE_SHARED_MEMORY */
@@ -555,6 +562,7 @@ no_init_message:
while (1) {
#ifdef T_USE_SHARED_MEMORY
wait_message();
+ __sync_synchronize();
#endif
#ifdef T_USE_SHARED_MEMORY
--
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