From 53499f5e9faecb1593f9a3de54385ac4ebd9aa83 Mon Sep 17 00:00:00 2001
From: Our Air Quality <info@ourairquality.org>
Date: Tue, 2 Jan 2018 11:49:09 -0600
Subject: [PATCH] timers: rework the core locking around timers (bug #52719)

Want the core lock held while working on the timer data structures.
---
 src/api/tcpip.c     |  2 --
 src/core/timeouts.c | 25 +++++++++++++++----------
 2 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/src/api/tcpip.c b/src/api/tcpip.c
index 6763a5cb..608ba607 100644
--- a/src/api/tcpip.c
+++ b/src/api/tcpip.c
@@ -99,11 +99,9 @@ tcpip_thread(void *arg)
 
   LOCK_TCPIP_CORE();
   while (1) {                          /* MAIN Loop */
-    UNLOCK_TCPIP_CORE();
     LWIP_TCPIP_THREAD_ALIVE();
     /* wait for a message, timeouts are processed while waiting */
     TCPIP_MBOX_FETCH(&mbox, (void **)&msg);
-    LOCK_TCPIP_CORE();
     if (msg == NULL) {
       LWIP_DEBUGF(TCPIP_DEBUG, ("tcpip_thread: invalid message: NULL\n"));
       LWIP_ASSERT("tcpip_thread: invalid message", 0);
diff --git a/src/core/timeouts.c b/src/core/timeouts.c
index 01e0d0ec..de5300ad 100644
--- a/src/core/timeouts.c
+++ b/src/core/timeouts.c
@@ -350,15 +350,7 @@ sys_check_timeouts(void)
 #endif /* LWIP_DEBUG_TIMERNAMES */
         memp_free(MEMP_SYS_TIMEOUT, tmptimeout);
         if (handler != NULL) {
-#if !NO_SYS
-          /* For LWIP_TCPIP_CORE_LOCKING, lock the core before calling the
-             timeout handler function. */
-          LOCK_TCPIP_CORE();
-#endif /* !NO_SYS */
           handler(arg);
-#if !NO_SYS
-          UNLOCK_TCPIP_CORE();
-#endif /* !NO_SYS */
         }
         LWIP_TCPIP_THREAD_ALIVE();
       }
@@ -416,16 +408,29 @@ sys_timeouts_sleeptime(void)
 void
 sys_timeouts_mbox_fetch(sys_mbox_t *mbox, void **msg)
 {
-  u32_t sleeptime;
+  u32_t sleeptime, res;
 
 again:
+  LWIP_ASSERT_CORE_LOCKED();
+
   if (!next_timeout) {
+    UNLOCK_TCPIP_CORE();
     sys_arch_mbox_fetch(mbox, msg, 0);
+    LOCK_TCPIP_CORE();
     return;
   }
 
   sleeptime = sys_timeouts_sleeptime();
-  if (sleeptime == 0 || sys_arch_mbox_fetch(mbox, msg, sleeptime) == SYS_ARCH_TIMEOUT) {
+  if (sleeptime == 0) {
+    sys_check_timeouts();
+    /* We try again to fetch a message from the mbox. */
+    goto again;
+  }
+
+  UNLOCK_TCPIP_CORE();
+  res = sys_arch_mbox_fetch(mbox, msg, sleeptime);
+  LOCK_TCPIP_CORE();
+  if (res == SYS_ARCH_TIMEOUT) {
     /* If a SYS_ARCH_TIMEOUT value is returned, a timeout occurred
        before a message could be fetched. */
     sys_check_timeouts();