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Add IFNET_HOLD reserved pointer value for the ifindex ifnet array,

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which allows an index to be reserved for an ifnet without making
the ifnet available for management operations.  Use this in if_alloc()
while the ifnet lock is released between initial index allocation and
completion of ifnet initialization.

Add ifindex_free() to centralize the implementation of releasing an
ifindex value.  Use in if_free() and if_vmove(), as well as when
releasing a held index in if_alloc().

Reviewed by:	bz
MFC after:	3 days
This commit is contained in:
Robert Watson 2009-08-26 11:13:10 +00:00
parent f9f231846a
commit ed2dabfc68
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=196559
1 changed files with 39 additions and 13 deletions
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52
sys/net/if.c
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@ -175,6 +175,13 @@ int ifqmaxlen = IFQ_MAXLEN;
struct rwlock ifnet_rwlock;
struct sx ifnet_sxlock;
/*
* The allocation of network interfaces is a rather non-atomic affair; we
* need to select an index before we are ready to expose the interface for
* use, so will use this pointer value to indicate reservation.
*/
#define IFNET_HOLD (void *)(uintptr_t)(-1)
static if_com_alloc_t *if_com_alloc[256];
static if_com_free_t *if_com_free[256];
@ -193,6 +200,8 @@ ifnet_byindex_locked(u_short idx)
if (idx > V_if_index)
return (NULL);
if (V_ifindex_table[idx].ife_ifnet == IFNET_HOLD)
return (NULL);
return (V_ifindex_table[idx].ife_ifnet);
}
@ -228,18 +237,18 @@ ifnet_byindex_ref(u_short idx)
* failure.
*/
static int
ifindex_alloc(u_short *idxp)
ifindex_alloc_locked(u_short *idxp)
{
u_short idx;
IFNET_WLOCK_ASSERT();
/*
* Try to find an empty slot below if_index. If we fail, take the
* Try to find an empty slot below V_if_index. If we fail, take the
* next slot.
*/
for (idx = 1; idx <= V_if_index; idx++) {
if (ifnet_byindex_locked(idx) == NULL)
if (V_ifindex_table[idx].ife_ifnet == NULL)
break;
}
@ -254,6 +263,27 @@ ifindex_alloc(u_short *idxp)
return (0);
}
static void
ifindex_free_locked(u_short idx)
{
IFNET_WLOCK_ASSERT();
V_ifindex_table[idx].ife_ifnet = NULL;
while (V_if_index > 0 &&
V_ifindex_table[V_if_index].ife_ifnet == NULL)
V_if_index--;
}
static void
ifindex_free(u_short idx)
{
IFNET_WLOCK();
ifindex_free_locked(idx);
IFNET_WUNLOCK();
}
static void
ifnet_setbyindex_locked(u_short idx, struct ifnet *ifp)
{
@ -370,11 +400,12 @@ if_alloc(u_char type)
ifp = malloc(sizeof(struct ifnet), M_IFNET, M_WAITOK|M_ZERO);
IFNET_WLOCK();
if (ifindex_alloc(&idx) != 0) {
if (ifindex_alloc_locked(&idx) != 0) {
IFNET_WUNLOCK();
free(ifp, M_IFNET);
return (NULL);
}
ifnet_setbyindex_locked(idx, IFNET_HOLD);
IFNET_WUNLOCK();
ifp->if_index = idx;
ifp->if_type = type;
@ -383,6 +414,7 @@ if_alloc(u_char type)
ifp->if_l2com = if_com_alloc[type](type, ifp);
if (ifp->if_l2com == NULL) {
free(ifp, M_IFNET);
ifindex_free(idx);
return (NULL);
}
}
@ -421,9 +453,7 @@ if_free_internal(struct ifnet *ifp)
KASSERT(ifp == ifnet_byindex_locked(ifp->if_index),
("%s: freeing unallocated ifnet", ifp->if_xname));
ifnet_setbyindex_locked(ifp->if_index, NULL);
while (V_if_index > 0 && ifnet_byindex_locked(V_if_index) == NULL)
V_if_index--;
ifindex_free_locked(ifp->if_index);
IFNET_WUNLOCK();
if (if_com_free[ifp->if_alloctype] != NULL)
@ -916,18 +946,14 @@ if_vmove(struct ifnet *ifp, struct vnet *new_vnet)
* or we'd lock on one vnet and unlock on another.
*/
IFNET_WLOCK();
ifnet_setbyindex_locked(ifp->if_index, NULL);
while (V_if_index > 0 && ifnet_byindex_locked(V_if_index) == NULL)
V_if_index--;
IFNET_WUNLOCK();
ifindex_free_locked(ifp->if_index);
/*
* Switch to the context of the target vnet.
*/
CURVNET_SET_QUIET(new_vnet);
IFNET_WLOCK();
if (ifindex_alloc(&idx) != 0) {
if (ifindex_alloc_locked(&idx) != 0) {
IFNET_WUNLOCK();
panic("if_index overflow");
}