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prevent nested multicast references, reworked locking

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This commit is contained in:
Joachim Bauch 2011-08-04 23:39:15 +02:00
parent 9d7368ae2d
commit 26041a8ed8
4 changed files with 21 additions and 34 deletions
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42
buffer.c
View File

@ -221,10 +221,11 @@ evbuffer_chain_free(struct evbuffer_chain *chain)
EVBUFFER_CHAIN_EXTRA( EVBUFFER_CHAIN_EXTRA(
struct evbuffer_multicast_parent, struct evbuffer_multicast_parent,
chain); chain);
EVUTIL_ASSERT(info->source != NULL);
EVUTIL_ASSERT(info->parent != NULL); EVUTIL_ASSERT(info->parent != NULL);
EVBUFFER_LOCK(info); EVBUFFER_LOCK(info->source);
evbuffer_chain_decref(info->parent); evbuffer_chain_decref(info->parent);
EVBUFFER_UNLOCK(info); _evbuffer_decref_and_unlock(info->source);
} }
mm_free(chain); mm_free(chain);
@ -325,11 +326,8 @@ static inline void
evbuffer_chain_decref(struct evbuffer_chain *chain) evbuffer_chain_decref(struct evbuffer_chain *chain)
{ {
EVUTIL_ASSERT(chain->refcnt > 0); EVUTIL_ASSERT(chain->refcnt > 0);
if (--chain->refcnt > 0) { --chain->refcnt;
return; // chain will be freed when parent buffer is released
}
evbuffer_chain_free(chain);
} }
struct evbuffer * struct evbuffer *
@ -837,28 +835,12 @@ APPEND_CHAIN_MULTICAST(struct evbuffer *dst, struct evbuffer *src)
return; return;
} }
extra = EVBUFFER_CHAIN_EXTRA(struct evbuffer_multicast_parent, tmp); extra = EVBUFFER_CHAIN_EXTRA(struct evbuffer_multicast_parent, tmp);
if (chain->flags & EVBUFFER_MULTICAST) { // reference source chain which now becomes immutable
// source chain is a reference itself _evbuffer_incref(src);
struct evbuffer_multicast_parent *info = extra->source = src;
EVBUFFER_CHAIN_EXTRA( evbuffer_chain_incref(chain);
struct evbuffer_multicast_parent, extra->parent = chain;
chain); chain->flags |= EVBUFFER_IMMUTABLE;
#ifndef _EVENT_DISABLE_THREAD_SUPPORT
extra->lock = info->lock;
#endif
EVBUFFER_LOCK(info);
evbuffer_chain_incref(info->parent);
EVBUFFER_UNLOCK(info);
extra->parent = info->parent;
} else {
// reference source chain which now becomes immutable
evbuffer_chain_incref(chain);
#ifndef _EVENT_DISABLE_THREAD_SUPPORT
extra->lock = src->lock;
#endif
extra->parent = chain;
chain->flags |= EVBUFFER_IMMUTABLE;
}
tmp->buffer_len = chain->buffer_len; tmp->buffer_len = chain->buffer_len;
tmp->misalign = chain->misalign; tmp->misalign = chain->misalign;
tmp->off = chain->off; tmp->off = chain->off;
@ -953,7 +935,7 @@ evbuffer_add_buffer_reference(struct evbuffer *outbuf, struct evbuffer *inbuf)
} }
for (; chain; chain = chain->next) { for (; chain; chain = chain->next) {
if ((chain->flags & (EVBUFFER_FILESEGMENT|EVBUFFER_SENDFILE)) != 0) { if ((chain->flags & (EVBUFFER_FILESEGMENT|EVBUFFER_SENDFILE|EVBUFFER_MULTICAST)) != 0) {
// chain type can not be referenced // chain type can not be referenced
result = -1; result = -1;
goto done; goto done;

5
evbuffer-internal.h
View File

@ -248,9 +248,8 @@ struct evbuffer_file_segment {
/** Information about the multicast parent of a chain. Lives at the /** Information about the multicast parent of a chain. Lives at the
* end of an evbuffer_chain with the EVBUFFER_MULTICAST flag set. */ * end of an evbuffer_chain with the EVBUFFER_MULTICAST flag set. */
struct evbuffer_multicast_parent { struct evbuffer_multicast_parent {
#ifndef _EVENT_DISABLE_THREAD_SUPPORT /** source buffer the multicast parent belongs to */
void *lock; /**< lock prevent concurrent access to the parent */ struct evbuffer *source;
#endif
/** multicast parent for this chain */ /** multicast parent for this chain */
struct evbuffer_chain *parent; struct evbuffer_chain *parent;
}; };

6
include/event2/buffer.h
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@ -393,11 +393,15 @@ int evbuffer_add_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf);
This is a non-destructive add. The data from one buffer is copied This is a non-destructive add. The data from one buffer is copied
into the other buffer. However, no unnecessary memory copies occur. into the other buffer. However, no unnecessary memory copies occur.
Note that buffers already containing buffer references can't be added
to other buffers.
@param outbuf the output buffer @param outbuf the output buffer
@param inbuf the input buffer @param inbuf the input buffer
@return 0 if successful, or -1 if an error occurred @return 0 if successful, or -1 if an error occurred
*/ */
int evbuffer_add_buffer_reference(struct evbuffer *outbuf, struct evbuffer *inbuf); int evbuffer_add_buffer_reference(struct evbuffer *outbuf,
struct evbuffer *inbuf);
/** /**
A cleanup function for a piece of memory added to an evbuffer by A cleanup function for a piece of memory added to an evbuffer by

2
test/regress_buffer.c
View File

@ -1544,7 +1544,9 @@ test_evbuffer_multicast(void *ptr)
tt_assert(buf2); tt_assert(buf2);
tt_int_op(evbuffer_add_buffer_reference(buf2, buf1), ==, 0); tt_int_op(evbuffer_add_buffer_reference(buf2, buf1), ==, 0);
// nested references are not allowed
tt_int_op(evbuffer_add_buffer_reference(buf2, buf2), ==, -1); tt_int_op(evbuffer_add_buffer_reference(buf2, buf2), ==, -1);
tt_int_op(evbuffer_add_buffer_reference(buf1, buf2), ==, -1);
// both buffers contain the same amount of data // both buffers contain the same amount of data
tt_int_op(evbuffer_get_length(buf1), ==, evbuffer_get_length(buf1)); tt_int_op(evbuffer_get_length(buf1), ==, evbuffer_get_length(buf1));