ich777/linux_media
1
0
Fork 0
mirror of https://github.com/tbsdtv/linux_media.git synced 2025-07-23 04:33:26 +02:00
Code Issues Packages Projects Releases Wiki Activity

rhashtable: move dereference inside rht_ptr()

Browse Source 
Rather than dereferencing a pointer to a bucket and then passing the
result to rht_ptr(), we now pass in the pointer and do the dereference
in rht_ptr().

This requires that we pass in the tbl and hash as well to support RCU
checks, and means that the various rht_for_each functions can expect a
pointer that can be dereferenced without further care.

There are two places where we dereference a bucket pointer
where there is no testable protection - in each case we know
that we much have exclusive access without having taken a lock.
The previous code used rht_dereference() to pretend that holding
the mutex provided protects, but holding the mutex never provides
protection for accessing buckets.

So instead introduce rht_ptr_exclusive() that can be used when
there is known to be exclusive access without holding any locks.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
NeilBrown
2019-04-12 11:52:08 +10:00
committed by David S. Miller
parent c5783311a1
commit adc6a3ab19
3 changed files with 49 additions and 34 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
lib/rhashtable.c
View File

@@ -231,7 +231,8 @@ static int rhashtable_rehash_one(struct rhashtable *ht,
err = -ENOENT;
rht_for_each_from(entry, rht_ptr(*bkt), old_tbl, old_hash) {
rht_for_each_from(entry, rht_ptr(bkt, old_tbl, old_hash),
old_tbl, old_hash) {
err = 0;
next = rht_dereference_bucket(entry->next, old_tbl, old_hash);
@@ -248,8 +249,7 @@ static int rhashtable_rehash_one(struct rhashtable *ht,
rht_lock_nested(new_tbl, &new_tbl->buckets[new_hash], SINGLE_DEPTH_NESTING);
head = rht_ptr(rht_dereference_bucket(new_tbl->buckets[new_hash],
new_tbl, new_hash));
head = rht_ptr(new_tbl->buckets + new_hash, new_tbl, new_hash);
RCU_INIT_POINTER(entry->next, head);
@@ -491,7 +491,7 @@ static void *rhashtable_lookup_one(struct rhashtable *ht,
int elasticity;
elasticity = RHT_ELASTICITY;
rht_for_each_from(head, rht_ptr(*bkt), tbl, hash) {
rht_for_each_from(head, rht_ptr(bkt, tbl, hash), tbl, hash) {
struct rhlist_head *list;
struct rhlist_head *plist;
@@ -557,7 +557,7 @@ static struct bucket_table *rhashtable_insert_one(struct rhashtable *ht,
if (unlikely(rht_grow_above_100(ht, tbl)))
return ERR_PTR(-EAGAIN);
head = rht_ptr(rht_dereference_bucket(*bkt, tbl, hash));
head = rht_ptr(bkt, tbl, hash);
RCU_INIT_POINTER(obj->next, head);
if (ht->rhlist) {
@@ -1139,7 +1139,7 @@ restart:
struct rhash_head *pos, *next;
cond_resched();
for (pos = rht_ptr(rht_dereference(*rht_bucket(tbl, i), ht)),
for (pos = rht_ptr_exclusive(rht_bucket(tbl, i)),
next = !rht_is_a_nulls(pos) ?
rht_dereference(pos->next, ht) : NULL;
!rht_is_a_nulls(pos);