Module Name: src
Committed By: thorpej
Date: Sun May 23 19:13:27 UTC 2021
Modified Files:
src/sys/arch/alpha/alpha: pmap.c
Log Message:
Fix a bug in pmap_tlb_shootdown_all_user(), where it was not
stashing away the pointer to the pmap in the TLB context structure
like pmap_tlb_shootdown() was doing. This would result in the
following failure scenario:
- Page fault handler calls pmap_enter() to map a page. Mapping
is the first one for that L2 PT L3 PT, meaning that an L2 PT
and an L3 PT must be allocated.
- L2 PT allocation succeeds.
- L3 PT allocation fails under memory pressure.
- pmap_enter() goes to drop the reference on the L2 PT, which, because
it was the first of its mappings, frees the L2 PT. Becuse PALcode
may have already tried to service a TLB miss though that L2 PT, we
must issue an all-user-VA shootdown, and call pmap_tlb_shootdown_all_user()
to do so.
- pmap_tlb_shootnow() is called and an assert fires because the TLB
context structure does not point to a pmap.
This did not fail in the pmap_remove() scenario because the TLB context
would have already had at least one call to pmap_tlb_shootdown(), which
was initializing the pmap pointer properly.
PR port-alpha/56200
To generate a diff of this commit:
cvs rdiff -u -r1.276 -r1.277 src/sys/arch/alpha/alpha/pmap.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/alpha/alpha/pmap.c
diff -u src/sys/arch/alpha/alpha/pmap.c:1.276 src/sys/arch/alpha/alpha/pmap.c:1.277
--- src/sys/arch/alpha/alpha/pmap.c:1.276 Sat Apr 3 15:29:02 2021
+++ src/sys/arch/alpha/alpha/pmap.c Sun May 23 19:13:27 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: pmap.c,v 1.276 2021/04/03 15:29:02 thorpej Exp $ */
+/* $NetBSD: pmap.c,v 1.277 2021/05/23 19:13:27 thorpej Exp $ */
/*-
* Copyright (c) 1998, 1999, 2000, 2001, 2007, 2008, 2020
@@ -135,7 +135,7 @@
#include <sys/cdefs.h> /* RCS ID & Copyright macro defns */
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.276 2021/04/03 15:29:02 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.277 2021/05/23 19:13:27 thorpej Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@@ -743,6 +743,9 @@ pmap_tlb_shootdown_all_user(pmap_t const
TLB_CTX_SET_FLAG(tlbctx, TLB_CTX_F_IMB);
}
+ KASSERT(tlbctx->t_pmap == NULL || tlbctx->t_pmap == pmap);
+ tlbctx->t_pmap = pmap;
+
TLB_CTX_SET_ALLVA(tlbctx);
}
