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xen/granttable: Refactor some code

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Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Annie Li <annie.li@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Annie Li 2011-11-22 09:58:47 +08:00 committed by Konrad Rzeszutek Wilk
parent 0f9f5a9588
commit b1e495b2fa
1 changed files with 10 additions and 5 deletions
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15
drivers/xen/grant-table.c
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@ -257,15 +257,17 @@ EXPORT_SYMBOL_GPL(gnttab_query_foreign_access);
static int gnttab_end_foreign_access_ref_v1(grant_ref_t ref, int readonly)
{
u16 flags, nflags;
u16 *pflags;
nflags = gnttab_shared.v1[ref].flags;
pflags = &gnttab_shared.v1[ref].flags;
nflags = *pflags;
do {
flags = nflags;
if (flags & (GTF_reading|GTF_writing)) {
printk(KERN_ALERT "WARNING: g.e. still in use!\n");
return 0;
}
} while ((nflags = sync_cmpxchg(&gnttab_shared.v1[ref].flags, flags, 0)) != flags);
} while ((nflags = sync_cmpxchg(pflags, flags, 0)) != flags);
return 1;
}
@ -316,20 +318,23 @@ static unsigned long gnttab_end_foreign_transfer_ref_v1(grant_ref_t ref)
{
unsigned long frame;
u16 flags;
u16 *pflags;
pflags = &gnttab_shared.v1[ref].flags;
/*
* If a transfer is not even yet started, try to reclaim the grant
* reference and return failure (== 0).
*/
while (!((flags = gnttab_shared.v1[ref].flags) & GTF_transfer_committed)) {
if (sync_cmpxchg(&gnttab_shared.v1[ref].flags, flags, 0) == flags)
while (!((flags = *pflags) & GTF_transfer_committed)) {
if (sync_cmpxchg(pflags, flags, 0) == flags)
return 0;
cpu_relax();
}
/* If a transfer is in progress then wait until it is completed. */
while (!(flags & GTF_transfer_completed)) {
flags = gnttab_shared.v1[ref].flags;
flags = *pflags;
cpu_relax();
}