lkml.org 
[lkml]   [2001]   [Sep]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [SOLVED + PATCH]: documented Oops running big-endian reiserfs on parisc architecture
On Tue, 4 Sep 2001, Ulrich Weigand wrote:
[SNIPPED...]

>
> If these instructions really *need* to be atomic, then reiserfs should
> ensure they are performed on properly aligned data, or else there might
> be subtle bugs even on Intel, because the operations will not actually
> be atomic (even though they don't trap).
>

Regardless of alignment, locked instructions in Intel machines are
atomic. Any "hidden" read/modify/write operations are performed
by the hardware, under the lock, preventing access by any other
CPUs or DMA.

> If you say that reiserfs doesn't really need these operations to be
> atomic because they run under other locks anyway, then they should not
> be using atomic operations in the first place; this will only cause
> unnecessary slowdown even on Intel.
>

Agreed that there are many "atomic_t" types on some drivers, and
"atomic" operations that don't need to be there. Unless a DMA operation
is in progress, anything executing under a spin-lock doesn't need
to be an "atomic" operation to make it, truly, atomic.

Cheers,
Dick Johnson

Penguin : Linux version 2.4.1 on an i686 machine (799.53 BogoMips).

I was going to compile a list of innovations that could be
attributed to Microsoft. Once I realized that Ctrl-Alt-Del
was handled in the BIOS, I found that there aren't any.


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:02    [W:0.054 / U:23.652 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site