Re: [PATCH] mmc: mmci: Do not release spinlock in request_end

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Jon Medhurst (Tixy) wrote:
On Thu, 2011-10-13 at 15:29 +0100, Russell King - ARM Linux wrote:
On Tue, Oct 11, 2011 at 04:06:41PM +0200, Ulf Hansson wrote:
The patch "mmc: core: move ->request() call from atomic context",
is the reason to why this change is possible. This simplifies the
error handling code execution path quite a lot and potentially also
fixes some error handling hang problems.

Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxxxxxx>
This doesn't look right:

void mmc_request_done(struct mmc_host *host, struct mmc_request *mrq)
{
        if (err && cmd->retries) {
                host->ops->request(host, mrq);


This is NOT how it looks at mmc-next. You need to test with Adrian Hunters patch which the commit refers two.

Linux next for mmc is available at:

git://dev.laptop.org/users/cjb/mmc mmc-next



So, not dropping the spinlock results in calling the request function
with the spinlock held - and as the request function then goes on to
lock the spinlock, we will deadlock.

Indeed, deadlock behaviour at this point is what I see with this patch
on a Versatile Express board running 3.0-rc9.


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