From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Rafael J. Wysocki" <rjw@sisk.pl>
Subject: Re: [PATCH] ACPI: EC: do transaction from interrupt context
Date: Fri, 26 Sep 2008 17:48:53 +0200
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References: <20080925170030.15311.27823.stgit@thinkpad> <200809261718.41641.rjw@sisk.pl> <48DCFE05.7050702@suse.de>
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To: Alexey Starikovskiy <astarikovskiy@suse.de>
Cc: Alexey Starikovskiy <aystarik@gmail.com>, "Zhao, Yakui" <yakui.zhao@intel.com>, Sitsofe Wheeler <sitsofe@yahoo.com>, LenBrown <lenb@kernel.org>, Linux-acpi@vger.kernel.org

On Friday, 26 of September 2008, Alexey Starikovskiy wrote:
> Rafael J. Wysocki wrote:
> >> He refers to the ec->curr (former ec->t).
> > 
> > Hm, I'm not sure what the failing scenario in this case would be.
> Last one was the thread of the stack is killed during transaction,
> thus stack vanishes and interrupt goes over freed memory.

This isn't possible IMO.  The thread is uninterruptible while waiting for the
transaction to finish (if I'm not mistaken).

That said, we can still embed 'curr' in 'struct acpi_ec' and do
'ec.curr = t' instead of 'ec->curr = &t' in acpi_ec_transaction_unlocked().
Now, if 'command' is embedded in 'curr', it will be sufficient to do
'if (curr.command)' instead of doing 'if (ec->curr)', wherever applicable.