pthread programming eats up resources (My or FreeBSD's fault?)

[David Xu]

On 2014/02/20 14:06, Erich Dollansky wrote:
> Hi,
>
> On Thu, 20 Feb 2014 13:41:08 +0800
> David Xu <davidxu at freebsd.org> wrote:
>
>> On 2014/02/19 02:06, Andre Albsmeier wrote:
>>
>> please compile it as static binary and run it, check if the
>> problem still exists, I am hunting the bug, it is not necessary in
>> the libthr because I have not changed its code for a long time.
>
> I just compiled is a static program. The behaviour is now different.
> The size still grows but much slower while 'res' stays below some 10MB.
>
> Size also got stagnant after some 2 min CPU time hanging around 126MB.
>
> I am running it on:
>
> FreeBSD X220.alogt.com 10.0-STABLE FreeBSD 10.0-STABLE #15 r261342: Sat
> Feb  1 14:52:39 WITA 2014
> erich at X220.alogt.com:/usr/obj/usr/src/sys/X220  amd64
>
> Erich
>

I have found the bug, it is in rtld, where malloc_aligned() is 
misfunctioning, memory can be corrupted by the function.

libthr calls _rtld_allocate_tls to allocate tls control block,
the function is in rtld, its uses malloc_aligned() which is not
working correctly.

Patch is attached.

Regards,
David Xu

-------------- next part --------------
Index: libexec/rtld-elf/xmalloc.c
===================================================================
--- libexec/rtld-elf/xmalloc.c	(revision 260700)
+++ libexec/rtld-elf/xmalloc.c	(working copy)
@@ -72,14 +72,10 @@
 malloc_aligned(size_t size, size_t align)
 {
 	void *mem, *res;
-	uintptr_t x;
-	size_t asize, r;
 
-	r = round(sizeof(void *), align);
-	asize = round(size, align) + r;
-	mem = xmalloc(asize);
-	x = (uintptr_t)mem;
-	res = (void *)round(x, align);
+	mem = xmalloc(size + sizeof(void *) + align - 1);
+	res =(void*)(((uintptr_t)mem + sizeof(void *) + align - 1) &
+		~(align - 1));
 	*(void **)((uintptr_t)res - sizeof(void *)) = mem;
 	return (res);
 }