/* From the reference implementation
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=drivers/xen/grant-table.c;hb=HEAD */
static unsigned long
gnttab_end_transfer(grant_ref_t ref)
{
unsigned long frame;
uint16_t flags;
uint16_t *pflags = &gnttab_table[ref].flags;
/*
* If a transfer is not even yet started, try to reclaim the grant
* reference and return failure (== 0).
*/
while (!((flags = *pflags) & GTF_transfer_committed)) {
if (synch_cmpxchg(pflags, flags, 0) == flags)
return 0;
}
/* If a transfer is in progress then wait until it is completed. */
while (!(flags & GTF_transfer_completed)) {
flags = *pflags;
}
rmb(); /* Read the frame number /after/ reading completion status. */
frame = gnttab_table[ref].frame;
BUG_ON(frame == 0);
return frame;
}
unsigned long
gnttab_end_foreign_transfer_ref(grant_ref_t ref)
{
unsigned long frame;
uint16_t flags;
/*
* If a transfer is not even yet started, try to reclaim the grant
* reference and return failure (== 0).
*/
while (!((flags = shared[ref].flags) & GTF_transfer_committed)) {
if ( synch_cmpxchg(&shared[ref].flags, flags, 0) == flags )
return (0);
cpu_spinwait();
}
/* If a transfer is in progress then wait until it is completed. */
while (!(flags & GTF_transfer_completed)) {
flags = shared[ref].flags;
cpu_spinwait();
}
/* Read the frame number /after/ reading completion status. */
rmb();
frame = shared[ref].frame;
KASSERT(frame != 0, ("grant table inconsistent"));
return (frame);
}
unsigned long
gnttab_end_transfer(grant_ref_t ref)
{
unsigned long frame;
uint16_t flags;
BUG_ON(ref >= NR_GRANT_ENTRIES || ref < NR_RESERVED_ENTRIES);
while (!((flags = gnttab_table[ref].flags) & GTF_transfer_committed)) {
if (synch_cmpxchg(&gnttab_table[ref].flags, flags, 0) == flags) {
printk("Release unused transfer grant.\n");
put_free_entry(ref);
return 0;
}
}
/* If a transfer is in progress then wait until it is completed. */
while (!(flags & GTF_transfer_completed)) {
flags = gnttab_table[ref].flags;
}
/* Read the frame number /after/ reading completion status. */
rmb();
frame = gnttab_table[ref].frame;
put_free_entry(ref);
return frame;
}
void grants_end_access(grant_ref_t ref)
{
uint16_t flags, nflags;
nflags = grant_entries[ref].flags;
do {
if ((flags = nflags) & (GTF_reading|GTF_writing))
fatal_error("grants_end_access: still in use\n");
} while ((nflags = synch_cmpxchg(&grant_entries[ref].flags, flags, 0)) != flags);
free_list[ref] = free_entry;
free_entry = ref;
}
int
gnttab_end_foreign_access_ref(grant_ref_t ref)
{
uint16_t flags, nflags;
nflags = shared[ref].flags;
do {
if ( (flags = nflags) & (GTF_reading|GTF_writing) ) {
printf("%s: WARNING: g.e. still in use!\n", __func__);
return (0);
}
} while ((nflags = synch_cmpxchg(&shared[ref].flags, flags, 0)) !=
flags);
return (1);
}
CAMLprim value
caml_gnttab_end_access(value v_ref)
{
grant_ref_t ref = Int_val(v_ref);
uint16_t flags, nflags;
BUG_ON(ref >= NR_GRANT_ENTRIES || ref < NR_RESERVED_ENTRIES);
nflags = gnttab_table[ref].flags;
do {
if ((flags = nflags) & (GTF_reading|GTF_writing)) {
printk("WARNING: g.e. %d still in use! (%x)\n", ref, flags);
return Val_unit;
}
} while ((nflags = synch_cmpxchg(&gnttab_table[ref].flags, flags, 0)) !=
flags);
return Val_unit;
}
int
gnttab_end_access(grant_ref_t ref)
{
uint16_t flags, nflags;
BUG_ON(ref >= NR_GRANT_ENTRIES || ref < NR_RESERVED_ENTRIES);
nflags = gnttab_table[ref].flags;
do {
if ((flags = nflags) & (GTF_reading|GTF_writing)) {
printk("WARNING: g.e. still in use! (%x)\n", flags);
return 0;
}
} while ((nflags = synch_cmpxchg(&gnttab_table[ref].flags, flags, 0)) !=
flags);
put_free_entry(ref);
return 1;
}
