Date: Tue, 20 Jun 2006 10:51:20 -0700 From: Jason Evans <jasone@FreeBSD.org> To: Ville-Pertti Keinonen <will@exomi.com> Cc: freebsd-current@freebsd.org, Krassimir Slavchev <krassi@bulinfo.net> Subject: Re: memory leak in free() Message-ID: <44983598.7010108@FreeBSD.org> In-Reply-To: <0D175ABD-B494-48BD-9DBD-349DE3712913@exomi.com> References: <448FC3AF.9060606@bulinfo.net> <200606141023.51185.jhb@freebsd.org> <449048C7.6090109@FreeBSD.org> <0D175ABD-B494-48BD-9DBD-349DE3712913@exomi.com>
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Ville-Pertti Keinonen wrote: > > On Jun 14, 2006, at 8:35 PM, Jason Evans wrote: > >> Incidentally, this isn't an issue on 64-bit systems, since only mmap >> () is used to request memory from the kernel. > > > The test does seem to leak memory on 64-bit systems, though; not the > actual allocated bits, but support structures, namely nodes that > chunk_dealloc tries to insert into old_chunks but fails because a node > holding that address is already there. > > It should be possible to fix this either by removing any nodes within > range from old_chunks when allocating "new" memory, or by checking the > return value of RB_INSERT in chunk_dealloc, and deallocating the new > node if it returns non-NULL. > > A patch implementing the latter that seems to work: > > --- malloc.c 10 May 2006 00:07:45 -0000 1.126 > +++ malloc.c 19 Jun 2006 13:58:57 -0000 > @@ -1370,7 +1370,8 @@ > node->chunk = (void *)((uintptr_t)chunk + (uintptr_t) > offset); > node->size = chunk_size; > - RB_INSERT(chunk_tree_s, &old_chunks, node); > + if (RB_INSERT(chunk_tree_s, &old_chunks, node) != NULL) > + base_chunk_node_dealloc(node); > } > #ifdef USE_BRK Ah, you are right that there is a leak. I'm going to use a slightly different approach to fixing the problem, but thank you very much for pointing it out. Jason
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