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Date:      Mon, 7 Aug 2017 17:29:55 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r322175 - head/sys/amd64/amd64
Message-ID:  <201708071729.v77HTtFa005747@repo.freebsd.org>
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Author: kib
Date: Mon Aug  7 17:29:54 2017
New Revision: 322175
URL: https://svnweb.freebsd.org/changeset/base/322175

Log:
  Avoid DI recursion when reclaim_pv_chunk() is called from
  pmap_advise() or pmap_remove().
  
  Reported and tested by:	pho (previous version)
  Reviewed by:	alc
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week

Modified:
  head/sys/amd64/amd64/pmap.c

Modified: head/sys/amd64/amd64/pmap.c
==============================================================================
--- head/sys/amd64/amd64/pmap.c	Mon Aug  7 17:29:48 2017	(r322174)
+++ head/sys/amd64/amd64/pmap.c	Mon Aug  7 17:29:54 2017	(r322175)
@@ -428,8 +428,15 @@ static struct lock_object invl_gen_ts = {
 	.lo_name = "invlts",
 };
 
+static bool
+pmap_not_in_di(void)
+{
+
+	return (curthread->td_md.md_invl_gen.gen == 0);
+}
+
 #define	PMAP_ASSERT_NOT_IN_DI() \
-    KASSERT(curthread->td_md.md_invl_gen.gen == 0, ("DI already started"))
+    KASSERT(pmap_not_in_di(), ("DI already started"))
 
 /*
  * Start a new Delayed Invalidation (DI) block of code, executed by
@@ -2856,6 +2863,19 @@ SYSCTL_INT(_vm_pmap, OID_AUTO, pv_entry_spare, CTLFLAG
 	"Current number of spare pv entries");
 #endif
 
+static void
+reclaim_pv_chunk_leave_pmap(pmap_t pmap, pmap_t locked_pmap, bool start_di)
+{
+
+	if (pmap == NULL)
+		return;
+	pmap_invalidate_all(pmap);
+	if (pmap != locked_pmap)
+		PMAP_UNLOCK(pmap);
+	if (start_di)
+		pmap_delayed_invl_finished();
+}
+
 /*
  * We are in a serious low memory condition.  Resort to
  * drastic measures to free some pages so we can allocate
@@ -2883,6 +2903,7 @@ reclaim_pv_chunk(pmap_t locked_pmap, struct rwlock **l
 	struct spglist free;
 	uint64_t inuse;
 	int bit, field, freed;
+	bool start_di;
 
 	PMAP_LOCK_ASSERT(locked_pmap, MA_OWNED);
 	KASSERT(lockp != NULL, ("reclaim_pv_chunk: lockp is NULL"));
@@ -2891,19 +2912,21 @@ reclaim_pv_chunk(pmap_t locked_pmap, struct rwlock **l
 	PG_G = PG_A = PG_M = PG_RW = 0;
 	SLIST_INIT(&free);
 	TAILQ_INIT(&new_tail);
-	pmap_delayed_invl_started();
+
+	/*
+	 * A delayed invalidation block should already be active if
+	 * pmap_advise() or pmap_remove() called this function by way
+	 * of pmap_demote_pde_locked().
+	 */
+	start_di = pmap_not_in_di();
+
 	mtx_lock(&pv_chunks_mutex);
 	while ((pc = TAILQ_FIRST(&pv_chunks)) != NULL && SLIST_EMPTY(&free)) {
 		TAILQ_REMOVE(&pv_chunks, pc, pc_lru);
 		mtx_unlock(&pv_chunks_mutex);
 		if (pmap != pc->pc_pmap) {
-			if (pmap != NULL) {
-				pmap_invalidate_all(pmap);
-				if (pmap != locked_pmap)
-					PMAP_UNLOCK(pmap);
-			}
-			pmap_delayed_invl_finished();
-			pmap_delayed_invl_started();
+			reclaim_pv_chunk_leave_pmap(pmap, locked_pmap,
+			    start_di);
 			pmap = pc->pc_pmap;
 			/* Avoid deadlock and lock recursion. */
 			if (pmap > locked_pmap) {
@@ -2920,6 +2943,8 @@ reclaim_pv_chunk(pmap_t locked_pmap, struct rwlock **l
 			PG_A = pmap_accessed_bit(pmap);
 			PG_M = pmap_modified_bit(pmap);
 			PG_RW = pmap_rw_bit(pmap);
+			if (start_di)
+				pmap_delayed_invl_started();
 		}
 
 		/*
@@ -2994,12 +3019,7 @@ reclaim_pv_chunk(pmap_t locked_pmap, struct rwlock **l
 	}
 	TAILQ_CONCAT(&pv_chunks, &new_tail, pc_lru);
 	mtx_unlock(&pv_chunks_mutex);
-	if (pmap != NULL) {
-		pmap_invalidate_all(pmap);
-		if (pmap != locked_pmap)
-			PMAP_UNLOCK(pmap);
-	}
-	pmap_delayed_invl_finished();
+	reclaim_pv_chunk_leave_pmap(pmap, locked_pmap, start_di);
 	if (m_pc == NULL && !SLIST_EMPTY(&free)) {
 		m_pc = SLIST_FIRST(&free);
 		SLIST_REMOVE_HEAD(&free, plinks.s.ss);

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