From: Ben Pfaff <blp@nicira.com>
Date: Tue, 24 Apr 2012 17:57:41 +0000 (-0700)
Subject: jsonrpc: Keep jsonrpc_recv() from taking over the CPU.
X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3a4548cfb2fb7e7344618f449ab9bf651ef83e6b;p=openvswitch

jsonrpc: Keep jsonrpc_recv() from taking over the CPU.

jsonrpc_recv() could take an unbounded amount of CPU time as long as data
kept arriving, preventing other work from taking place.  This limits the
amount of work to processing at most 25 kB of received data and then
yielding to the caller.

Signed-off-by: Ben Pfaff <blp@nicira.com>
---

diff --git a/lib/jsonrpc.c b/lib/jsonrpc.c
index fc8a75b0..4ebff104 100644
--- a/lib/jsonrpc.c
+++ b/lib/jsonrpc.c
@@ -277,13 +277,19 @@ jsonrpc_send(struct jsonrpc *rpc, struct jsonrpc_msg *msg)
 int
 jsonrpc_recv(struct jsonrpc *rpc, struct jsonrpc_msg **msgp)
 {
+    int i;
+
     *msgp = NULL;
     if (rpc->status) {
         return rpc->status;
     }
 
-    while (!rpc->received) {
-        if (byteq_is_empty(&rpc->input)) {
+    for (i = 0; i < 50; i++) {
+        if (rpc->received) {
+            *msgp = rpc->received;
+            rpc->received = NULL;
+            return 0;
+        } else if (byteq_is_empty(&rpc->input)) {
             size_t chunk;
             int retval;
 
@@ -328,9 +334,7 @@ jsonrpc_recv(struct jsonrpc *rpc, struct jsonrpc_msg **msgp)
         }
     }
 
-    *msgp = rpc->received;
-    rpc->received = NULL;
-    return 0;
+    return EAGAIN;
 }
 
 /* Causes the poll loop to wake up when jsonrpc_recv() may return a value other