Author: markj
Date: Tue Dec 1 16:06:31 2020
New Revision: 368236
URL: https://svnweb.freebsd.org/changeset/base/368236
Log:
vmem: Revert r364744
A pair of bugs are believed to have caused the hangs described in the
commit log message for r364744:
1. uma_reclaim() could trigger reclamation of the reserve of boundary
tags used to avoid deadlock. This was fixed by r366840.
2. The loop in vmem_xalloc() would in some cases try to allocate more
boundary tags than the expected upper bound of BT_MAXALLOC. The
reserve is sized based on the value BT_MAXMALLOC, so this behaviour
could deplete the reserve without guaranteeing a successful
allocation, resulting in a hang. This was fixed by r366838.
PR: 248008
Tested by: rmacklem
Modified:
head/sys/kern/subr_vmem.c
Modified: head/sys/kern/subr_vmem.c
==============================================================================
--- head/sys/kern/subr_vmem.c Tue Dec 1 16:02:52 2020 (r368235)
+++ head/sys/kern/subr_vmem.c Tue Dec 1 16:06:31 2020 (r368236)
@@ -706,14 +706,10 @@ vmem_startup(void)
vmem_zone = uma_zcreate("vmem",
sizeof(struct vmem), NULL, NULL, NULL, NULL,
UMA_ALIGN_PTR, 0);
-#ifdef UMA_MD_SMALL_ALLOC
vmem_bt_zone = uma_zcreate("vmem btag",
sizeof(struct vmem_btag), NULL, NULL, NULL, NULL,
UMA_ALIGN_PTR, UMA_ZONE_VM);
-#else
- vmem_bt_zone = uma_zcreate("vmem btag",
- sizeof(struct vmem_btag), NULL, NULL, NULL, NULL,
- UMA_ALIGN_PTR, UMA_ZONE_VM | UMA_ZONE_NOFREE);
+#ifndef UMA_MD_SMALL_ALLOC
mtx_init(&vmem_bt_lock, "btag lock", NULL, MTX_DEF);
uma_prealloc(vmem_bt_zone, BT_MAXALLOC);
/*
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