What do people think about adding the following macro to <sys/queue.h>?
(I don't care much about the name, just the functionality)
#define TAILQ_FOREACH_TMP(var, tmp, head, field) \
for ((var) = TAILQ_FIRST((head)); \
(var) && (((tmp) = TAILQ_NEXT((var), field)) || 1); \
(var) = (tmp))
Essentially, this provides a traversal of the tailq that is safe
from element removal, while being simple to drop in to those sections
of the code that need updating, as evidenced in the patch below.
--
Jonathan
Index: uthread_kern.c
===================================================================
RCS file: /ncvs/src/lib/libc_r/uthread/uthread_kern.c,v
retrieving revision 1.40
diff -u -r1.40 uthread_kern.c
--- uthread_kern.c 2002/02/09 19:58:41 1.40
+++ uthread_kern.c 2002/07/02 14:52:00
@@ -664,7 +664,7 @@
int kern_pipe_added = 0;
int nfds = 0;
int timeout_ms = 0;
- struct pthread *pthread;
+ struct pthread *pthread, *pthread_next;
struct timespec ts;
struct timeval tv;
@@ -746,7 +746,7 @@
}
PTHREAD_WAITQ_SETACTIVE();
- TAILQ_FOREACH(pthread, &_workq, qe) {
+ TAILQ_FOREACH_TMP(pthread, pthread_next, &_workq, qe) {
switch (pthread->state) {
case PS_SPINBLOCK:
/*
@@ -858,7 +858,7 @@
* _poll syscall:
*/
PTHREAD_WAITQ_SETACTIVE();
- TAILQ_FOREACH(pthread, &_workq, qe) {
+ TAILQ_FOREACH_TMP(pthread, pthread_next, &_workq, qe) {
switch (pthread->state) {
case PS_SPINBLOCK:
/*
@@ -947,7 +947,7 @@
* that is now available.
*/
PTHREAD_WAITQ_SETACTIVE();
- TAILQ_FOREACH(pthread, &_workq, qe) {
+ TAILQ_FOREACH_TMP(pthread, pthread_next, &_workq, qe) {
if (pthread->state == PS_SPINBLOCK) {
/*
* If the lock is available, let the thread run.
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