Hi,
I would like to better integrate rtdk and the posix skin by forcibly
wrapping the calls to malloc/free and also wrap printf to call
rt_printf.
However, currently, rt_printf can not really be used as a drop-in
replacement of printf:
- it is necessary to call rt_printf_auto_init, we can do it in the
library init code;
- the first rt_printf causes a memory allocation, so a potential switch
to secondary mode, which is what using rt_printf was trying to avoid in
the first place.
In order to solve this second issue, and to avoid forcibly creating a
buffer for each thread, which would be wasteful, here is a patch, which,
following an idea of Philippe, creates a pool of pre-allocated buffers.
The pool is handled in a lockless fashion, using xnarch_atomic_cmpxchg
(so, will only work with CONFIG_XENO_FASTSYNCH).
diff --git a/src/rtdk/rt_print.c b/src/rtdk/rt_print.c
index 93b711a..2ed2209 100644
--- a/src/rtdk/rt_print.c
+++ b/src/rtdk/rt_print.c
@@ -30,6 +30,8 @@
#include <rtdk.h>
#include <asm/xenomai/system.h>
#include <asm-generic/stack.h>
+#include <asm/xenomai/atomic.h>
+#include <asm-generic/bits/current.h>
#define RT_PRINT_BUFFER_ENV "RT_PRINT_BUFFER"
#define RT_PRINT_DEFAULT_BUFFER 16*1024
@@ -37,6 +39,9 @@
#define RT_PRINT_PERIOD_ENV "RT_PRINT_PERIOD"
#define RT_PRINT_DEFAULT_PERIOD 100 /* ms */
+#define RT_PRINT_BUFFERS_COUNT_ENV "RT_PRINT_BUFFERS_COUNT"
+#define RT_PRINT_DEFAULT_BUFFERS_COUNT 4
+
#define RT_PRINT_LINE_BREAK 256
#define RT_PRINT_SYSLOG_STREAM NULL
@@ -63,6 +68,9 @@ struct print_buffer {
* caching on SMP.
*/
off_t read_pos;
+#ifdef CONFIG_XENO_FASTSYNCH
+ struct print_buffer *pool_next;
+#endif /* CONFIG_XENO_FASTSYNCH */
};
static struct print_buffer *first_buffer;
@@ -75,6 +83,17 @@ static pthread_mutex_t buffer_lock;
static pthread_cond_t printer_wakeup;
static pthread_key_t buffer_key;
static pthread_t printer_thread;
+#ifdef CONFIG_XENO_FASTSYNCH
+static xnarch_atomic_t buffer_pool;
+static unsigned pool_capacity;
+static xnarch_atomic_t pool_count;
+
+#define buf_pool_set(buf) xnarch_atomic_set(&buffer_pool, (unsigned long)buf)
+#define buf_pool_get() (struct print_buffer *)xnarch_atomic_get(&buffer_pool)
+#define buf_pool_cmpxchg(oldval, newval) \
+ ((struct print_buffer *)xnarch_atomic_cmpxchg \
+ (&buffer_pool, (unsigned long)oldval, (unsigned long)newval))
+#endif /* CONFIG_XENO_FASTSYNCH */
static void cleanup_buffer(struct print_buffer *buffer);
static void print_buffers(void);
@@ -243,43 +262,28 @@ static void set_buffer_name(struct print_buffer *buffer,
const char *name)
}
}
-int rt_print_init(size_t buffer_size, const char *buffer_name)
+static struct print_buffer *rt_print_init_inner(size_t size)
{
- struct print_buffer *buffer = pthread_getspecific(buffer_key);
- size_t size = buffer_size;
-
- if (!size)
- size = default_buffer_size;
- else if (size < RT_PRINT_LINE_BREAK)
- return EINVAL;
+ struct print_buffer *buffer;
- if (buffer) {
- /* Only set name if buffer size is unchanged or default */
- if (size == buffer->size || !buffer_size) {
- set_buffer_name(buffer, buffer_name);
- return 0;
- }
- cleanup_buffer(buffer);
- }
+ assert_nrt();
buffer = malloc(sizeof(*buffer));
if (!buffer)
- return ENOMEM;
+ return NULL;
buffer->ring = malloc(size);
if (!buffer->ring) {
free(buffer);
- return ENOMEM;
+ return NULL;
}
+ buffer->size = size;
+
memset(buffer->ring, 0, size);
buffer->read_pos = 0;
buffer->write_pos = 0;
- buffer->size = size;
-
- set_buffer_name(buffer, buffer_name);
-
buffer->prev = NULL;
pthread_mutex_lock(&buffer_lock);
@@ -294,6 +298,52 @@ int rt_print_init(size_t buffer_size, const char
*buffer_name)
pthread_mutex_unlock(&buffer_lock);
+ return buffer;
+}
+
+int rt_print_init(size_t buffer_size, const char *buffer_name)
+{
+ struct print_buffer *buffer = pthread_getspecific(buffer_key);
+ size_t size = buffer_size;
+
+ if (!size)
+ size = default_buffer_size;
+ else if (size < RT_PRINT_LINE_BREAK)
+ return EINVAL;
+
+ if (buffer) {
+ /* Only set name if buffer size is unchanged or default */
+ if (size == buffer->size || !buffer_size) {
+ set_buffer_name(buffer, buffer_name);
+ return 0;
+ }
+ cleanup_buffer(buffer);
+ buffer = NULL;
+ }
+
+#ifdef CONFIG_XENO_FASTSYNCH
+ if (xeno_get_current() != XN_NO_HANDLE &&
+ !(xeno_get_current_mode() & XNRELAX) && buf_pool_get()) {
+ struct print_buffer *old;
+
+ old = buf_pool_get();
+ while (old != buffer) {
+ buffer = old;
+ old = buf_pool_cmpxchg(buffer, buffer->pool_next);
+ }
+ if (buffer)
+ xnarch_atomic_dec(&pool_count);
+ }
+#endif /* CONFIG_XENO_FASTSYNCH */
+
+ if (!buffer)
+ buffer = rt_print_init_inner(size);
+
+ if (!buffer)
+ return ENOMEM;
+
+ set_buffer_name(buffer, buffer_name);
+
pthread_setspecific(buffer_key, buffer);
return 0;
@@ -346,12 +396,36 @@ static void cleanup_buffer(struct print_buffer *buffer)
{
struct print_buffer *prev, *next;
+ assert_nrt();
+
pthread_setspecific(buffer_key, NULL);
pthread_mutex_lock(&buffer_lock);
print_buffers();
+ pthread_mutex_unlock(&buffer_lock);
+
+#ifdef CONFIG_XENO_FASTSYNCH
+ {
+ struct print_buffer *old;
+
+ old = buf_pool_get();
+ buffer->pool_next = buffer;
+ while (old != buffer->next
+ && xnarch_atomic_get(&pool_count) < pool_capacity) {
+ buffer->next = old;
+ old = buf_pool_cmpxchg(buffer->pool_next, buffer);
+ }
+ if (old == buffer->pool_next) {
+ xnarch_atomic_inc(&pool_count);
+ return;
+ }
+ }
+#endif /* CONFIG_XENO_FASTSYNCH */
+
+ pthread_mutex_lock(&buffer_lock);
+
prev = buffer->prev;
next = buffer->next;
@@ -523,6 +597,39 @@ void __rt_print_init(void)
print_period.tv_sec = period / 1000;
print_period.tv_nsec = (period % 1000) * 1000000;
+#ifdef CONFIG_XENO_FASTSYNCH
+ {
+ unsigned i;
+
+ pool_capacity = RT_PRINT_DEFAULT_BUFFERS_COUNT;
+
+ value_str = getenv(RT_PRINT_BUFFERS_COUNT_ENV);
+ if (value_str) {
+ errno = 0;
+ pool_capacity = strtoul(value_str, NULL, 0);
+ if (errno) {
+ fprintf(stderr, "Invalid %s\n",
+ RT_PRINT_BUFFERS_COUNT_ENV);
+ exit(1);
+ }
+ }
+ for (i = 0; i < pool_capacity; i++) {
+ struct print_buffer *buffer;
+
+ buffer = rt_print_init_inner(default_buffer_size);
+ if (!buffer) {
+ fprintf(stderr, "Error allocating rt_printf "
+ "buffer\n");
+ exit(1);
+ }
+
+ buffer->pool_next = buf_pool_get();
+ buf_pool_set(buffer);
+ }
+ xnarch_atomic_set(&pool_count, pool_capacity);
+ }
+#endif /* CONFIG_XENO_FASTSYNCH */
+
pthread_mutex_init(&buffer_lock, NULL);
pthread_key_create(&buffer_key, (void (*)(void*))cleanup_buffer);
--
Gilles.
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