D60658.id.diff
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	diff --git a/sys/kern/kern_rmlock.c b/sys/kern/kern_rmlock.c
	--- a/sys/kern/kern_rmlock.c
	+++ b/sys/kern/kern_rmlock.c
	@@ -875,7 +875,9 @@
	*
	* Neither rms_rlock nor rms_runlock use thread fences. Instead interrupt
	* fences are inserted to ensure ordering with the code executed in the IPI
	- * handler.
	+ * handler. Writers interrupt all CPUs both to block readers and to unblock
	+ * them, so a reader that sees no writer also sees what the last writer
	+ * stored.
	*
	* No attempt is made to track which CPUs read locked at least once,
	* consequently write locking sends IPIs to all of them. This will become a
	@@ -1171,7 +1173,7 @@
	#endif

	static void
	-rms_wlock_switch(struct rmslock *rms)
	+rms_block_readers(struct rmslock *rms)
	{
	struct rmslock_ipi rmsipi;

	@@ -1188,6 +1190,19 @@
	&rmsipi.srcra);
	}

	+/*
	+ * Order the writer's stores before the count readers check without a fence.
	+ */
	+static void
	+rms_unblock_readers(struct rmslock *rms)
	+{
	+
	+ MPASS(rms->readers == 0);
	+ MPASS(rms->writers == 1);
	+
	+ cpus_fence_seq_cst();
	+}
	+
	void
	rms_wlock(struct rmslock *rms)
	{
	@@ -1210,7 +1225,7 @@
	KASSERT(rms->owner == RMS_NOOWNER,
	("%s: unexpected owner value %p\n", __func__, rms->owner));

	- rms_wlock_switch(rms);
	+ rms_block_readers(rms);
	rms_assert_no_pcpu_readers(rms);

	if (rms->readers > 0) {
	@@ -1235,6 +1250,8 @@
	("%s: unexpected owner value %p\n", __func__, rms->owner));
	MPASS(rms->writers >= 1);
	MPASS(rms->readers == 0);
	+ if (rms->writers == 1)
	+ rms_unblock_readers(rms);
	rms->writers--;
	if (rms->writers > 0) {
	wakeup_one(&rms->owner);