git: 942951ba46ec - main - uma dbg: catch more corruption with atomics

[Ryan Libby]

The branch main has been updated by rlibby:

URL: https://cgit.FreeBSD.org/src/commit/?id=942951ba46ecd5ebab18de006a24dc52e2d3f745

commit 942951ba46ecd5ebab18de006a24dc52e2d3f745
Author:     Ryan Libby <rlibby at FreeBSD.org>
AuthorDate: 2020-12-31 21:02:45 +0000
Commit:     Ryan Libby <rlibby at FreeBSD.org>
CommitDate: 2020-12-31 21:02:45 +0000

    uma dbg: catch more corruption with atomics
    
    Use atomic testandset and testandclear to catch concurrent double free,
    and to reduce the number of atomic operations.
    
    Submitted by:   jeff
    Reviewed by:    cem, kib, markj (all previous version)
    Sponsored by:   Dell EMC Isilon
    Differential Revision:  https://reviews.freebsd.org/D22703
---
 sys/vm/uma_core.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/sys/vm/uma_core.c b/sys/vm/uma_core.c
index a0192642205d..39c846effac8 100644
--- a/sys/vm/uma_core.c
+++ b/sys/vm/uma_core.c
@@ -5392,10 +5392,10 @@ uma_dbg_alloc(uma_zone_t zone, uma_slab_t slab, void *item)
 	keg = zone->uz_keg;
 	freei = slab_item_index(slab, keg, item);
 
-	if (BIT_ISSET(keg->uk_ipers, freei, slab_dbg_bits(slab, keg)))
+	if (BIT_TEST_SET_ATOMIC(keg->uk_ipers, freei,
+	    slab_dbg_bits(slab, keg)))
 		panic("Duplicate alloc of %p from zone %p(%s) slab %p(%d)",
 		    item, zone, zone->uz_name, slab, freei);
-	BIT_SET_ATOMIC(keg->uk_ipers, freei, slab_dbg_bits(slab, keg));
 }
 
 /*
@@ -5426,11 +5426,10 @@ uma_dbg_free(uma_zone_t zone, uma_slab_t slab, void *item)
 		panic("Unaligned free of %p from zone %p(%s) slab %p(%d)",
 		    item, zone, zone->uz_name, slab, freei);
 
-	if (!BIT_ISSET(keg->uk_ipers, freei, slab_dbg_bits(slab, keg)))
+	if (!BIT_TEST_CLR_ATOMIC(keg->uk_ipers, freei,
+	    slab_dbg_bits(slab, keg)))
 		panic("Duplicate free of %p from zone %p(%s) slab %p(%d)",
 		    item, zone, zone->uz_name, slab, freei);
-
-	BIT_CLR_ATOMIC(keg->uk_ipers, freei, slab_dbg_bits(slab, keg));
 }
 #endif /* INVARIANTS */