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gnrc_rpl: Lock against race against initializer thread

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When gnrc_rpl_init was called from a thread with higher priority than
the RPL thread, the initializer's call to gnrc_netreg_register would be
executed before the event loop even had a chance to set up its message
queue.

The added short-lived lock makes it work from threads of any priority.
This commit is contained in:
chrysn 2020-10-12 10:03:02 +02:00
parent be93529c89
commit 7ed50c3d18
1 changed files with 17 additions and 3 deletions
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18
sys/net/gnrc/routing/rpl/gnrc_rpl.c
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@ -69,17 +69,24 @@ kernel_pid_t gnrc_rpl_init(kernel_pid_t if_pid)
{
/* check if RPL was initialized before */
if (gnrc_rpl_pid == KERNEL_PID_UNDEF) {
mutex_t eventloop_startup = MUTEX_INIT_LOCKED;
_instance_id = 0;
/* start the event loop */
gnrc_rpl_pid = thread_create(_stack, sizeof(_stack), GNRC_RPL_PRIO,
THREAD_CREATE_STACKTEST,
_event_loop, NULL, "RPL");
_event_loop, (void*)&eventloop_startup,
"RPL");
if (gnrc_rpl_pid == KERNEL_PID_UNDEF) {
DEBUG("RPL: could not start the event loop\n");
return KERNEL_PID_UNDEF;
}
/* Wait for the event loop to indicate that it set up its message
* queue, and registration with netreg can commence. */
mutex_lock(&eventloop_startup);
_me_reg.demux_ctx = ICMPV6_RPL_CTRL;
_me_reg.target.pid = gnrc_rpl_pid;
/* register interest in all ICMPv6 packets */
@ -246,9 +253,16 @@ static void *_event_loop(void *args)
{
msg_t msg, reply;
(void)args;
{
mutex_t *eventloop_startup = (mutex_t*)args;
msg_init_queue(_msg_q, GNRC_RPL_MSG_QUEUE_SIZE);
/* Message queue is initialized, gnrc_rpl_init can continue and will
* pop the underlying mutex off its stack. */
mutex_unlock(eventloop_startup);
}
/* preinitialize ACK */
reply.type = GNRC_NETAPI_MSG_TYPE_ACK;