On 8/15/2007 10:18 AM, Heiko Carstens wrote:
> On Wed, Aug 15, 2007 at 02:49:03PM +0800, Herbert Xu wrote:
>> Chris Snook <[email protected]> wrote:
>> >
>> > Because atomic operations are generally used for synchronization, which requires
>> > volatile behavior. Most such codepaths currently use an inefficient barrier().
>> > Some forget to and we get bugs, because people assume that atomic_read()
>> > actually reads something, and atomic_write() actually writes something. Worse,
>> > these are architecture-specific, even compiler version-specific bugs that are
>> > often difficult to track down.
>>
>> I'm yet to see a single example from the current tree where
>> this patch series is the correct solution. So far the only
>> example has been a buggy piece of code which has since been
>> fixed with a cpu_relax.
>
> Btw.: we still have
>
> include/asm-i386/mach-es7000/mach_wakecpu.h: while (!atomic_read(deassert));
> include/asm-i386/mach-default/mach_wakecpu.h: while (!atomic_read(deassert));
>
> Looks like they need to be fixed as well.
I don't know if this here is affected:
/* drivers/ieee1394/ieee1394_core.h */
static inline unsigned int get_hpsb_generation(struct hpsb_host *host)
{
return atomic_read(&host->generation);
}
/* drivers/ieee1394/nodemgr.c */
static int nodemgr_host_thread(void *__hi)
{
[...]
for (;;) {
[... sleep until bus reset event ...]
/* Pause for 1/4 second in 1/16 second intervals,
* to make sure things settle down. */
g = get_hpsb_generation(host);
for (i = 0; i < 4 ; i++) {
if (msleep_interruptible(63) ||
kthread_should_stop())
goto exit;
/* Now get the generation in which the node ID's we collect
* are valid. During the bus scan we will use this generation
* for the read transactions, so that if another reset occurs
* during the scan the transactions will fail instead of
* returning bogus data. */
generation = get_hpsb_generation(host);
/* If we get a reset before we are done waiting, then
* start the waiting over again */
if (generation != g)
g = generation, i = 0;
}
[... scan bus, using generation ...]
}
exit:
[...]
}
--
Stefan Richter
-=====-=-=== =--- -====
http://arcgraph.de/sr/
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