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Date: Tue, 14 Aug 2012 13:47:35 -0700 From: Mike Waychison <mikew@...gle.com> To: Seiji Aguchi <seiji.aguchi@....com> Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>, "Matthew Garrett (mjg@...hat.com)" <mjg@...hat.com>, "dzickus@...hat.com" <dzickus@...hat.com>, "dle-develop@...ts.sourceforge.net" <dle-develop@...ts.sourceforge.net>, Satoru Moriya <satoru.moriya@....com> Subject: Re: efi_pstore: question about how to remove create_sysfs_entry() from a write callback. On Tue, Aug 14, 2012 at 12:29 PM, Seiji Aguchi <seiji.aguchi@....com> 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: linux-kernel-owner@...r.kernel.org [mailto:linux-kernel-owner@...r.kernel.org] On Behalf Of Seiji Aguchi >> Sent: Tuesday, August 14, 2012 2:52 PM >> To: Mike Waychison >> Cc: linux-kernel@...r.kernel.org; Luck, Tony (tony.luck@...el.com); Matthew Garrett (mjg@...hat.com); dzickus@...hat.com; dle- >> develop@...ts.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 >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More >> majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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