Hello,
I finally got around to rebasing some patches, and realised that the
patch from Simon Guinot below still gets rebased over torvalds' v4.4 .
Any reason it was not applied ?
Or was the issue fixed in another, non-git-conflicting way ? (I see
nothing recent in git log kernel/resource.c)
I do not find a trace of a mail confirming that I tested it and that it
fixes the issue. So here goes:
Tested-by: Vincent Pelletier <plr.vinc...@gmail.com>
Testing details: bug reproduced on 4.1, patch applied over 4.1 and bug
disappeared. After rebasing this patch (along with others) over 4.4,
bug does not reappear. I did not try to reproduce bug with 4.4, but if
preferred I can give it a go.
On Thu, 10 Sep 2015 00:15:18 +0200, Simon Guinot
<simon.gui...@sequanux.org> wrote:
> In __request_region, if a conflict with a BUSY and MUXED resource is
> detected, then the caller goes to sleep and waits for the resource to
> be released. A pointer on the conflicting resource is kept. At wake-up
> this pointer is used as a parent to retry to request the region. A first
> problem is that this pointer might well be invalid (if for example the
> conflicting resource have already been freed). An another problem is
> that the next call to __request_region() fails to detect a remaining
> conflict. The previously conflicting resource is passed as a parameter
> and __request_region() will look for a conflict among the children of
> this resource and not at the resource itself. It is likely to succeed
> anyway, even if there is still a conflict. Instead, the parent of the
> conflicting resource should be passed to __request_region().
>
> As a fix attempt, this patch don't update the parent resource pointer in
> the case we have to wait for a muxed region right after.
>
> Reported-by: Vincent Pelletier <plr.vinc...@gmail.com>
> Signed-off-by: Simon Guinot <simon.gui...@sequanux.org>
> Tested-by: Vincent Donnefort <vdonnef...@gmail.com>
> ---
> kernel/resource.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/resource.c b/kernel/resource.c
> index fed052a1bc9f..b8c84804db6a 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -1072,9 +1072,10 @@ struct resource * __request_region(struct resource
> *parent,
> if (!conflict)
> break;
> if (conflict != parent) {
> - parent = conflict;
> - if (!(conflict->flags & IORESOURCE_BUSY))
> + if (!(conflict->flags & IORESOURCE_BUSY)) {
> + parent = conflict;
> continue;
> + }
> }
> if (conflict->flags & flags & IORESOURCE_MUXED) {
> add_wait_queue(&muxed_resource_wait, &wait);
Regards,
--
Vincent Pelletier
