Replace cv_{timed}wait_sig with cv_{timed}wait_idle where appropriate

There are a number of places where cv_?_sig is used simply for
accounting purposes but the surrounding code has no ability to
cope with actually receiving a signal. On FreeBSD it is possible
to send signals to individual kernel threads so this could
enable undesirable behavior.

This patch adds routines on Linux that will do the same idle
accounting as _sig without making the task interruptible. On
FreeBSD cv_*_idle  are all aliases for cv_*

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Closes #10843

module/zfs/arc.c

@@ -9174,7 +9174,7 @@ l2arc_feed_thread(void *unused)
 	cookie = spl_fstrans_mark();
 	while (l2arc_thread_exit == 0) {
 		CALLB_CPR_SAFE_BEGIN(&cpr);
-		(void) cv_timedwait_sig(&l2arc_feed_thr_cv,
+		(void) cv_timedwait_idle(&l2arc_feed_thr_cv,
 		    &l2arc_feed_thr_lock, next);
 		CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
 		next = ddi_get_lbolt() + hz;

module/zfs/dbuf.c

@@ -718,7 +718,7 @@ dbuf_evict_thread(void *unused)
 	while (!dbuf_evict_thread_exit) {
 		while (!dbuf_cache_above_lowater() && !dbuf_evict_thread_exit) {
 			CALLB_CPR_SAFE_BEGIN(&cpr);
-			(void) cv_timedwait_sig_hires(&dbuf_evict_cv,
+			(void) cv_timedwait_idle_hires(&dbuf_evict_cv,
 			    &dbuf_evict_lock, SEC2NSEC(1), MSEC2NSEC(1), 0);
 			CALLB_CPR_SAFE_END(&cpr, &dbuf_evict_lock);
 		}

module/zfs/mmp.c

@@ -671,7 +671,7 @@ mmp_thread(void *arg)
 		}
 
 		CALLB_CPR_SAFE_BEGIN(&cpr);
-		(void) cv_timedwait_sig_hires(&mmp->mmp_thread_cv,
+		(void) cv_timedwait_idle_hires(&mmp->mmp_thread_cv,
 		    &mmp->mmp_thread_lock, next_time, USEC2NSEC(100),
 		    CALLOUT_FLAG_ABSOLUTE);
 		CALLB_CPR_SAFE_END(&cpr, &mmp->mmp_thread_lock);

module/zfs/txg.c

@@ -242,16 +242,11 @@ txg_thread_wait(tx_state_t *tx, callb_cpr_t *cpr, kcondvar_t *cv, clock_t time)
 {
 	CALLB_CPR_SAFE_BEGIN(cpr);
 
-	/*
-	 * cv_wait_sig() is used instead of cv_wait() in order to prevent
-	 * this process from incorrectly contributing to the system load
-	 * average when idle.
-	 */
 	if (time) {
-		(void) cv_timedwait_sig(cv, &tx->tx_sync_lock,
+		(void) cv_timedwait_idle(cv, &tx->tx_sync_lock,
 		    ddi_get_lbolt() + time);
 	} else {
-		cv_wait_sig(cv, &tx->tx_sync_lock);
+		cv_wait_idle(cv, &tx->tx_sync_lock);
 	}
 
 	CALLB_CPR_SAFE_END(cpr, &tx->tx_sync_lock);
@@ -760,7 +755,8 @@ txg_wait_open(dsl_pool_t *dp, uint64_t txg, boolean_t should_quiesce)
 		if (should_quiesce == B_TRUE) {
 			cv_wait_io(&tx->tx_quiesce_done_cv, &tx->tx_sync_lock);
 		} else {
-			cv_wait_sig(&tx->tx_quiesce_done_cv, &tx->tx_sync_lock);
+			cv_wait_idle(&tx->tx_quiesce_done_cv,
+			    &tx->tx_sync_lock);
 		}
 	}
 	mutex_exit(&tx->tx_sync_lock);

module/zfs/vdev_trim.c

@@ -481,7 +481,7 @@ vdev_trim_range(trim_args_t *ta, uint64_t start, uint64_t size)
 	if (ta->trim_type == TRIM_TYPE_MANUAL) {
 		while (vd->vdev_trim_rate != 0 && !vdev_trim_should_stop(vd) &&
 		    vdev_trim_calculate_rate(ta) > vd->vdev_trim_rate) {
-			cv_timedwait_sig(&vd->vdev_trim_io_cv,
+			cv_timedwait_idle(&vd->vdev_trim_io_cv,
 			    &vd->vdev_trim_io_lock, ddi_get_lbolt() +
 			    MSEC_TO_TICK(10));
 		}

module/zfs/zthr.c

@@ -237,15 +237,10 @@ zthr_procedure(void *arg)
 			t->zthr_func(t->zthr_arg, t);
 			mutex_enter(&t->zthr_state_lock);
 		} else {
-			/*
-			 * cv_wait_sig() is used instead of cv_wait() in
-			 * order to prevent this process from incorrectly
-			 * contributing to the system load average when idle.
-			 */
 			if (t->zthr_sleep_timeout == 0) {
-				cv_wait_sig(&t->zthr_cv, &t->zthr_state_lock);
+				cv_wait_idle(&t->zthr_cv, &t->zthr_state_lock);
 			} else {
-				(void) cv_timedwait_sig_hires(&t->zthr_cv,
+				(void) cv_timedwait_idle_hires(&t->zthr_cv,
 				    &t->zthr_state_lock, t->zthr_sleep_timeout,
 				    MSEC2NSEC(1), 0);
 			}