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Bug 1124973 (part 3) - Use PL_DHashTableSearch() in nsHostResolver.cpp. r=froydnj,sworkman.

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Currently nsHostResolver.cpp uses PL_DHashTableLookup() and fails to use
PL_DHASH_ENTRY_IS_{FREE,BUSY} on the result the way it should. However, I think
it gets away with this because it always does this on the result:

  if (!he || !he->rec) { /* do stuff with |he->rec| */ }

The |!he| test is useless and always fails, but the |!he->rec| does the right
thing because (a) entry storage is always zeroed when the table is created, (b)
HostDB_ClearEntry() zeroes the |rec| field (via NS_RELEASE). So unused entries
always have a null |rec| field.

Furthermore, |he->rec| is never zero in a used entry because HostDB_InitEntry
always assigns it with a nsHostRecord assigned with infallible new in
nsHostRecord::Create (and there are existing assertions to this effect).

All this means that when this patch switches PL_DHashTableLookup to
PL_DHashTableSearch it can drop the |!he->rec| test and just do this:

  if (!he) { /* do stuff with |he->rec| */ }

Finally, there's a comment about HostDB_InitEntry failing which is bogus
because HostDB_InitEntry cannot fail. This patch fixes that too.

--HG--
extra : rebase_source : ded6f8ff404cb160d89bbe7deeb3b863249bdb94
This commit is contained in:
Nicholas Nethercote 2015-01-22 21:25:44 -08:00
parent 3163cfc2c1
commit c801affedb
1 changed files with 6 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
netwerk/dns/nsHostResolver.cpp
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@ -758,8 +758,8 @@ nsHostResolver::ResolveHost(const char *host,
nsHostDBEnt *he = static_cast<nsHostDBEnt *>
(PL_DHashTableAdd(&mDB, &key));
// if the record is null, then HostDB_InitEntry failed.
if (!he || !he->rec) {
// if the record is null, the hash table OOM'd.
if (!he) {
LOG((" Out of memory: no cache entry for [%s].\n", host));
rv = NS_ERROR_OUT_OF_MEMORY;
}
@ -834,7 +834,6 @@ nsHostResolver::ResolveHost(const char *host,
(unspecHe && unspecHe->rec),
"Valid host entries should contain a record");
if (unspecHe &&
unspecHe->rec &&
unspecHe->rec->HasUsableResult(TimeStamp::NowLoRes(), flags)) {
MOZ_ASSERT(unspecHe->rec->addr_info || unspecHe->rec->negative,
@ -956,8 +955,8 @@ nsHostResolver::DetachCallback(const char *host,
nsHostKey key = { host, flags, af };
nsHostDBEnt *he = static_cast<nsHostDBEnt *>
(PL_DHashTableLookup(&mDB, &key));
if (he && he->rec) {
(PL_DHashTableSearch(&mDB, &key));
if (he) {
// walk list looking for |callback|... we cannot assume
// that it will be there!
PRCList *node = he->rec->callbacks.next;
@ -1304,8 +1303,8 @@ nsHostResolver::CancelAsyncRequest(const char *host,
// Lookup the host record associated with host, flags & address family
nsHostKey key = { host, flags, af };
nsHostDBEnt *he = static_cast<nsHostDBEnt *>
(PL_DHashTableLookup(&mDB, &key));
if (he && he->rec) {
(PL_DHashTableSearch(&mDB, &key));
if (he) {
nsHostRecord* recPtr = nullptr;
PRCList *node = he->rec->callbacks.next;
// Remove the first nsDNSAsyncRequest callback which matches the