Hello Geert, On Wednesday, December 10, 2008 you wrote: > On Tue, 9 Dec 2008, Yuri Tikhonov wrote: >> The following patch fixes divide-by-zero error for the >> cases of really big PAGE_SIZEs (e.g. 256KB on ppc44x). >> Support for such big page sizes on 44x is not present in the >> current kernel yet, but coming soon. >> >> Also this patch fixes the comment for the max_threads >> settings, as this didn't match the things actually done >> in the code. >> >> Signed-off-by: Yuri Tikhonov <[EMAIL PROTECTED]> >> Signed-off-by: Ilya Yanok <[EMAIL PROTECTED]> >> --- >> kernel/fork.c | 8 ++++++-- >> 1 files changed, 6 insertions(+), 2 deletions(-) >> >> diff --git a/kernel/fork.c b/kernel/fork.c >> index 2a372a0..b0ac2fb 100644 >> --- a/kernel/fork.c >> +++ b/kernel/fork.c >> @@ -181,10 +181,14 @@ void __init fork_init(unsigned long mempages) >> >> /* >> * The default maximum number of threads is set to a safe >> - * value: the thread structures can take up at most half >> - * of memory. >> + * value: the thread structures can take up at most >> + * (1/8) part of memory. >> */ >> +#if (8 * THREAD_SIZE) > PAGE_SIZE >> max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); >> +#else >> + max_threads = mempages * PAGE_SIZE / (8 * THREAD_SIZE); > ^^^^^^^^^^^^^^^^^^^^ >> +#endif
> Can't this overflow, e.g. on 32-bit machines with HIGHMEM? The multiplier here is not PAGE_SIZE, but [PAGE_SIZE / (8 * THREAD_SIZE)], and this value is expected to be rather small (2, 4, or so). Furthermore, due to the #if/#endif construction multiplication is used only with rather big PAGE_SIZE values, and the bigger page size is then the smaller 'mempages' is. So, for example, when running with PAGE_SIZE=256KB, THREAD_SIZE=8KB, on 32-bit 440spe-based machine with 4GB RAM installed, here we have: max_threads = (4G/256K) * (256K / 8 * 8K) = 16384 * 4 = 65536. And the overflow will have a place only in case of very very big sizes of RAM: >= 256TB: max_threads = (256T / 256K) * (256K / 8 * 8K) = 0x4000.0000 * 4. But I don't think that with 256TB RAM installed this code will be the only place of problems :) Regards, Yuri -- Yuri Tikhonov, Senior Software Engineer Emcraft Systems, www.emcraft.com _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
