On 10/18/2016 11:54 PM, Luis R. Rodriguez wrote:
> On Tue, Oct 18, 2016 at 03:30:45PM +0200, Daniel Wagner wrote:
>> On 10/10/2016 10:37 PM, Luis R. Rodriguez wrote:
>>
>>>> fw_get_fileystem_firmware()
>>>> fw_finish_direct_load()
>>>> complete_all()
>>>>
>>>>
>>>> 2nd request (waiter context)
>>>>
>>>> _request_firmware()
>>>> _request_firmware_prepare()
>>>> fw_lookup_allocate_buf() # finds previously allocated buf
>>>> # returns 1 -> wait for loading
>>>> sync_cached_firmware_buf()
>>>> wait_for_completion_interruptible_timeout()
>>>
>>> No, that's wait_for_completion_interruptible() not
>>> wait_for_completion_interruptible_timeout()
>>
>> I confused that one from _request_firmware_load().
>
> Right and wait_for_completion_interruptible() has no timeout.
All wait_for_completion_*() function are small wrappers around
a common implemention. I thought that would be a clever idea to
reuse here, but from our discussion I see it isn't. My bad.
static int fw_umh_wait_timeout(struct fw_umh *fw_umh, long timeout)
{
int ret;
ret = wait_for_completion_interruptible_timeout(&fw_umh->completion,
timeout);
if (ret != 0 && test_bit(FW_UMH_ABORTED, &fw_umh->status))
return -ENOENT;
return ret;
}
long __sched
wait_for_completion_interruptible_timeout(struct completion *x,
unsigned long timeout)
{
return wait_for_common(x, timeout, TASK_INTERRUPTIBLE);
}
int __sched wait_for_completion_interruptible(struct completion *x)
{
long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE);
if (t == -ERESTARTSYS)
return t;
return 0;
}
I think it is far better to do something like:
static __fw_umh_wait_common(struct fw_umh *fw_umh, long timeout) { ... }
#define fw_umh_wait(fw_umh) __fw_umh_wait_common(fw_umh, MAX_SCHEDULE_TIMEOUT)
#define fw_umh_wait_timeout(fw_umh, timeout) __fw_umh_wait_common(fw_umh,
timeout)
(The function prefixes will be different, since umh isn't right as discussed.)
>>> Also note that we only call sync_cached_firmware_buf()
>>> *iff* fw_lookup_and_allocate_buf() returned the 1 -- I mentioned
>>> when this happens above. That happens only if we already had the entry on
>>> the fw cache. As it stands -- concurrent calls against the same fw name
>>> could cause a clash here, as such, the wait_for_completion_interruptible()
>>> is indeed still needed.
>>>
>>> Further optimizations can be considered later but for indeed, agreed
>>> that completion is needed even for the direct fw load case. The timeout
>>> though, I don't see a reason for it.
>>
>> So I think I found the source of the confusion about fw_umh_wait_timeout().
>> When providing a timeout value of 0 you get the
>> wait_for_completion_interruptible() version.
>
> I fail to see that, how so? Note that 0 does is not allowed anyway:
>
> static inline long firmware_loading_timeout(void)
> {
> return loading_timeout > 0 ? loading_timeout * HZ : MAX_JIFFY_OFFSET;
> }
Correct. The fw_umh_wait_timeout(0) is hard coded in sync_cached_firmware_buf().
fw_umh_wait_timeout(fw_umh, firmware_loading_timeout()) is used
_request_firmware_load().
I'll update the series and hopefully we get this all sorted out in the new
version.
cheers,
daniel
