Thread (14 messages) 14 messages, 5 authors, 2008-12-19

Re: [PATCH][v2] fork_init: fix division by zero

From: Paul Mackerras <hidden>
Date: 2008-12-12 00:49:40
Also in: lkml

Andrew Morton writes:
quoted
+#if (8 * THREAD_SIZE) > PAGE_SIZE
 	max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
+#else
+	max_threads = mempages * (PAGE_SIZE / (8 * THREAD_SIZE));
+#endif
The expression you've chosen here can be quite inacccurate, because
((PAGE_SIZE / (8 * THREAD_SIZE)) is a small number.  The way to
preserve accuracy is
The assumption is that THREAD_SIZE is a power of 2, as is PAGE_SIZE.

I think Yuri should be increasing THREAD_SIZE for the larger page
sizes he's implementing, because we have on-stack arrays whose size
depends on the page size.  I suspect that having THREAD_SIZE less than
1/8 of PAGE_SIZE risks stack overflows, and the better fix is for Yuri
to make sure THREAD_SIZE is at least 1/8 of PAGE_SIZE.  (In fact, more
may be needed - someone should work out what fraction is actually
needed.)

Paul.
Keyboard shortcuts
hback out one level
jnext message in thread
kprevious message in thread
ldrill in
Escclose help / fold thread tree
?toggle this help