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authorDave Barach <dave@barachs.net>2016-10-04 16:53:56 -0400
committerDamjan Marion <dmarion.lists@gmail.com>2016-10-05 07:44:47 +0000
commite91836368cec2ffed47743dc5626e2d0c44fc0ea (patch)
tree2963dd4e18d6da168b79e2bf6785b4d851284076
parent15977efc454a2faba91eca0184251dc8e0d553f0 (diff)
Fix mutex/condvar sleep when adding API msgs, VPP-461
Simply put, threads cannot sleep waiting for the vlib memory api main input queue to drain. If, say, thread i (i !=0) fills the vlib api main input queue with rpc requests - and then blocks trying to add another request - the game is over. RPCs attempt a barrier synchronization, which fails with Pr = {1.0} because thread i is in a mutex/condvar sleep. Add a main-thread cut-through path, which directly invokes the RPC callback function when called on the main thread. Change-Id: Ib036f0cc43b5738455c3a111cff64a132537152e Signed-off-by: Dave Barach <dave@barachs.net>
-rw-r--r--vlib-api/vlibmemory/memory_vlib.c41
1 files changed, 39 insertions, 2 deletions
diff --git a/vlib-api/vlibmemory/memory_vlib.c b/vlib-api/vlibmemory/memory_vlib.c
index 22ca0f3c889..ca3eb141f7e 100644
--- a/vlib-api/vlibmemory/memory_vlib.c
+++ b/vlib-api/vlibmemory/memory_vlib.c
@@ -1366,16 +1366,53 @@ vl_api_rpc_call_main_thread (void *fp, u8 * data, u32 data_length)
vl_api_rpc_call_t *mp;
api_main_t *am = &api_main;
vl_shmem_hdr_t *shmem_hdr = am->shmem_hdr;
+ unix_shared_memory_queue_t *q;
+
+ /* Main thread: call the function directly */
+ if (os_get_cpu_number () == 0)
+ {
+ vlib_main_t *vm = vlib_get_main ();
+ void (*call_fp) (void *);
+
+ vlib_worker_thread_barrier_sync (vm);
+
+ call_fp = fp;
+ call_fp (data);
+ vlib_worker_thread_barrier_release (vm);
+ return;
+ }
+
+ /* Any other thread, actually do an RPC call... */
mp = vl_msg_api_alloc_as_if_client (sizeof (*mp) + data_length);
+
memset (mp, 0, sizeof (*mp));
clib_memcpy (mp->data, data, data_length);
mp->_vl_msg_id = ntohs (VL_API_RPC_CALL);
mp->function = pointer_to_uword (fp);
mp->need_barrier_sync = 1;
- /* Use the "normal" control-plane mechanism for the main thread */
- vl_msg_api_send_shmem (shmem_hdr->vl_input_queue, (u8 *) & mp);
+ /*
+ * Use the "normal" control-plane mechanism for the main thread.
+ * Well, almost. if the main input queue is full, we cannot
+ * block. Otherwise, we can expect a barrier sync timeout.
+ */
+ q = shmem_hdr->vl_input_queue;
+
+ while (pthread_mutex_trylock (&q->mutex))
+ vlib_worker_thread_barrier_check ();
+
+ while (PREDICT_FALSE (unix_shared_memory_queue_is_full (q)))
+ {
+ pthread_mutex_unlock (&q->mutex);
+ vlib_worker_thread_barrier_check ();
+ while (pthread_mutex_trylock (&q->mutex))
+ vlib_worker_thread_barrier_check ();
+ }
+
+ vl_msg_api_send_shmem_nolock (q, (u8 *) & mp);
+
+ pthread_mutex_unlock (&q->mutex);
}
#define foreach_rpc_api_msg \