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From: Seiji Aguchi <seiji.aguchi@hds.com>
To: Mike Waychison <mikew@google.com>
CC: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Luck, Tony (tony.luck@intel.com)" <tony.luck@intel.com>,
        "Matthew Garrett (mjg@redhat.com)" <mjg@redhat.com>,
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        "dle-develop@lists.sourceforge.net" 
	<dle-develop@lists.sourceforge.net>,
        Satoru Moriya <satoru.moriya@hds.com>
Subject: RE: efi_pstore: question about how to remove create_sysfs_entry()
 from a write callback.
Thread-Topic: efi_pstore: question about how to remove create_sysfs_entry()
 from a write callback.
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Date: Tue, 14 Aug 2012 19:29:26 +0000
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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>
 
 } while()
 
 spin_lock_irqrestore(&efivars_lock);

  efivars_create_sysfs_entries();

Seiji

> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel-owner@vger.kernel.org] On Behalf Of Seiji Aguchi
> Sent: Tuesday, August 14, 2012 2:52 PM
> To: Mike Waychison
> Cc: linux-kernel@vger.kernel.org; Luck, Tony (tony.luck@intel.com); Matthew Garrett (mjg@redhat.com); dzickus@redhat.com; dle-
> develop@lists.sourceforge.net; 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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