From 111bce93de7ddf13a71ad6b5f80c92b725aff7b3 Mon Sep 17 00:00:00 2001 From: Taylor R Campbell Date: Thu, 31 Mar 2022 02:44:36 +0000 Subject: [PATCH 44/49] select(9): Use membar_acquire/release and atomic_store_release. No store-before-load ordering here -- this was obviously always intended to be load-before-load/store all along. --- sys/kern/sys_select.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/sys/kern/sys_select.c b/sys/kern/sys_select.c index 8e23ef4114ef..891984d67304 100644 --- a/sys/kern/sys_select.c +++ b/sys/kern/sys_select.c @@ -282,7 +282,7 @@ sel_do_scan(const char *opname, void *fds, const int nf, const size_t ni, l->l_selflag = SEL_SCANNING; } ncoll = sc->sc_ncoll; - membar_exit(); + membar_release(); if (opname == selop_select) { error = selscan((char *)fds, nf, ni, retval); @@ -653,7 +653,7 @@ selrecord(lwp_t *selector, struct selinfo *sip) * barrier to ensure that we access sel_lwp (above) before * other fields - this guards against a call to selclear(). */ - membar_enter(); + membar_acquire(); sip->sel_lwp = selector; SLIST_INSERT_HEAD(&selector->l_selwait, sip, sel_chain); /* Copy the argument, which is for selnotify(). */ @@ -872,9 +872,8 @@ selclear(void) * globally visible. */ next = SLIST_NEXT(sip, sel_chain); - membar_exit(); /* Release the record for another named waiter to use. */ - sip->sel_lwp = NULL; + atomic_store_release(&sip->sel_lwp, NULL); } mutex_spin_exit(lock); }