On Tue, Aug 14, 2012 at 12:29 PM, Seiji Aguchi <[email protected]> wrote:
> Mike,
>
> Previous pseudo code was not correct.
> More precisely, it is as follows.
> But, we still need to alloc memory dynamically in the part of <Save
> information about new entry>
> because a workqueue can't know how many new entries in advance.
>
> spin_lock_irqsave(&efivars_lock);
>
> do {
> get_next_variable();
> if (found new entry)
> <Save information about new entry>
If the work item is changed to instead do a loop, storage for this may
be saved elsewhere, either the stack (though 1KiB is sorta pushing it)
or on the heap.
>
> } while()
>
> spin_lock_irqrestore(&efivars_lock);
>
> efivars_create_sysfs_entries();
Something like this (pseudo) may work:
/* Loop until we have all entries in efivars. */
while (1) {
variable_name = kzalloc(1024, GFP_KERNEL );
spin_lock_irqsave(&efivars->lock);
bool found = false;
while (1) {
ret = ops->get_next_variable(variable_name)
if (ret == EFI_NOT_FOUND)
break;
if (!variable_is_already_present(variable, &efivars->list) {
found = true;
break;
}
}
if (!found) {
kfree(variable_name);
break;
}
<Register in sysfs>
}
If we are calling into pstore_info ops though from interrupt context,
it seems we'll need to fix the immediate problem of updating the
locking throughout to be interrupt safe.
>
> Seiji
>
>> -----Original Message-----
>> From: [email protected]
>> [mailto:[email protected]] On Behalf Of Seiji Aguchi
>> Sent: Tuesday, August 14, 2012 2:52 PM
>> To: Mike Waychison
>> Cc: [email protected]; Luck, Tony ([email protected]); Matthew
>> Garrett ([email protected]); [email protected]; dle-
>> [email protected]; Satoru Moriya
>> Subject: RE: efi_pstore: question about how to remove create_sysfs_entry()
>> from a write callback.
>>
>> > Can we not serialize this with &efivars->lock if it is updated to
>> > disable interrupts? A loop in the workqueue that locks, iterates
>> > through
>> > ->get_next_variable, and compares against searches in
>> > efivars->list should work, no?
>>
>> If my understanding is correct, your pseudo code is as follows.
>>
>> spin_lock_irqsave(&efivars_lock);
>>
>> do {
>> get_next_variable();
>> if (found new entry)
>> efivars_create_sysfs_entries();
>>
>> } while()
>>
>> spin_lock_irqrestore(&efivars_lock);
>>
>> But, memory is allocated dynamically with kzalloc() in
>> efivars_create_sysfs_entries().
>> I don't want to allocate memory while holding spin_lock.
>>
>> Please let me know if I'm missing something.
>>
>> Seiji
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