Stefan Fuhrmann wrote on Sat, Jun 11, 2011 at 10:13:27 +0200: > On 10.06.2011 22:28, Daniel Shahaf wrote: > >stef...@apache.org wrote on Wed, May 25, 2011 at 22:20:25 -0000: > >>Author: stefan2 > >>Date: Wed May 25 22:20:25 2011 > >>New Revision: 1127709 > >> > >>URL: http://svn.apache.org/viewvc?rev=1127709&view=rev > >>Log: > >>Fix a pool usage issue: svn_cache__get_partial() may be called many > >>times in a row. Thus, the internal pool used to construct keys should > >>be cleared in this function as well from time to time. > >> > >>* subversion/libsvn_subr/cache-membuffer.c > >> (svn_membuffer_cache_get_partial): regularly clear the internal scratch > >> pool > >> > >>Modified: > >> subversion/trunk/subversion/libsvn_subr/cache-membuffer.c > >> > >>Modified: subversion/trunk/subversion/libsvn_subr/cache-membuffer.c > >>URL: > >>http://svn.apache.org/viewvc/subversion/trunk/subversion/libsvn_subr/cache-membuffer.c?rev=1127709&r1=1127708&r2=1127709&view=diff > >>============================================================================== > >>--- subversion/trunk/subversion/libsvn_subr/cache-membuffer.c (original) > >>+++ subversion/trunk/subversion/libsvn_subr/cache-membuffer.c Wed May 25 > >>22:20:25 2011 > >>@@ -1668,6 +1668,12 @@ svn_membuffer_cache_get_partial(void **v > >> > >> DEBUG_CACHE_MEMBUFFER_INIT_TAG > >> > >>+ if (++cache->alloc_counter> ALLOCATIONS_PER_POOL_CLEAR) > >>+ { > >>+ apr_pool_clear(cache->pool); > >>+ cache->alloc_counter = 0; > >>+ } > >>+ > >Does this need to be guarded by a cache lock? > > > No. This happens in the outer / front-end code > that merely adds a key prefix (combine_key below) > before calling the shared cache object. > > All front-end operations assume single-threaded > access, which should be o.k. for fs_t-local objects.
Okay, if that function is guaranteed (perhaps by API contract) not to run concurrently to any other `front end' function (and in particular to itself), then my concerns are resolved. (I was worried about accessing cache->pool and cache->alloc_counter from multiple threads concurrently --- writer-writer or writer-reader --- which might to undefined behaviour.) What guarantees the single-threaded access? I don't see it documented in svn_cache.h (on the contrary, that one has explicit 'thread_safe' parameters) and the code doesn't take a lock at at that point either. > >> combine_key(cache->prefix, > >> sizeof(cache->prefix), > >> key, > > > -- Stefan^2.
