Author: markj
Date: Mon Nov 2 14:30:55 2020
New Revision: 367272
URL: https://svnweb.freebsd.org/changeset/base/367272
Log:
MFC r366838:
vmem: Allocate btags before looping in vmem_xalloc()
Modified:
stable/12/sys/kern/subr_vmem.c
Directory Properties:
stable/12/ (props changed)
Modified: stable/12/sys/kern/subr_vmem.c
==============================================================================
--- stable/12/sys/kern/subr_vmem.c Mon Nov 2 14:01:33 2020
(r367271)
+++ stable/12/sys/kern/subr_vmem.c Mon Nov 2 14:30:55 2020
(r367272)
@@ -359,6 +359,24 @@ bt_free(vmem_t *vm, bt_t *bt)
}
/*
+ * Hide MAXALLOC tags before dropping the arena lock to ensure that a
+ * concurrent allocation attempt does not grab them.
+ */
+static void
+bt_save(vmem_t *vm)
+{
+ KASSERT(vm->vm_nfreetags >= BT_MAXALLOC,
+ ("%s: insufficient free tags %d", __func__, vm->vm_nfreetags));
+ vm->vm_nfreetags -= BT_MAXALLOC;
+}
+
+static void
+bt_restore(vmem_t *vm)
+{
+ vm->vm_nfreetags += BT_MAXALLOC;
+}
+
+/*
* freelist[0] ... [1, 1]
* freelist[1] ... [2, 2]
* :
@@ -886,16 +904,11 @@ vmem_import(vmem_t *vm, vmem_size_t size, vmem_size_t
if (vm->vm_limit != 0 && vm->vm_limit < vm->vm_size + size)
return (ENOMEM);
- /*
- * Hide MAXALLOC tags so we're guaranteed to be able to add this
- * span and the tag we want to allocate from it.
- */
- MPASS(vm->vm_nfreetags >= BT_MAXALLOC);
- vm->vm_nfreetags -= BT_MAXALLOC;
+ bt_save(vm);
VMEM_UNLOCK(vm);
error = (vm->vm_importfn)(vm->vm_arg, size, flags, &addr);
VMEM_LOCK(vm);
- vm->vm_nfreetags += BT_MAXALLOC;
+ bt_restore(vm);
if (error)
return (ENOMEM);
@@ -1023,19 +1036,23 @@ vmem_try_fetch(vmem_t *vm, const vmem_size_t size, vme
*/
if (vm->vm_qcache_max != 0 || vm->vm_reclaimfn != NULL) {
avail = vm->vm_size - vm->vm_inuse;
+ bt_save(vm);
VMEM_UNLOCK(vm);
if (vm->vm_qcache_max != 0)
qc_drain(vm);
if (vm->vm_reclaimfn != NULL)
vm->vm_reclaimfn(vm, flags);
VMEM_LOCK(vm);
+ bt_restore(vm);
/* If we were successful retry even NOWAIT. */
if (vm->vm_size - vm->vm_inuse > avail)
return (1);
}
if ((flags & M_NOWAIT) != 0)
return (0);
+ bt_save(vm);
VMEM_CONDVAR_WAIT(vm);
+ bt_restore(vm);
return (1);
}
@@ -1083,13 +1100,14 @@ vmem_xalloc_nextfit(vmem_t *vm, const vmem_size_t size
error = ENOMEM;
VMEM_LOCK(vm);
-retry:
+
/*
* Make sure we have enough tags to complete the operation.
*/
if (bt_fill(vm, flags) != 0)
goto out;
+retry:
/*
* Find the next free tag meeting our constraints. If one is found,
* perform the allocation.
@@ -1364,15 +1382,14 @@ vmem_xalloc(vmem_t *vm, const vmem_size_t size0, vmem_
*/
first = bt_freehead_toalloc(vm, size, strat);
VMEM_LOCK(vm);
- for (;;) {
- /*
- * Make sure we have enough tags to complete the
- * operation.
- */
- error = bt_fill(vm, flags);
- if (error != 0)
- break;
+ /*
+ * Make sure we have enough tags to complete the operation.
+ */
+ error = bt_fill(vm, flags);
+ if (error != 0)
+ goto out;
+ for (;;) {
/*
* Scan freelists looking for a tag that satisfies the
* allocation. If we're doing BESTFIT we may encounter
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