Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Tue, 29 Mar 2016 20:18:22 +0100 | Subject | [PATCH 3.2 32/62] kernel/resource.c: fix muxed resource handling in __request_region() |
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3.2.79-rc1 review patch. If anyone has any objections, please let me know.
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From: Simon Guinot <simon.guinot@sequanux.org>
commit 59ceeaaf355fa0fb16558ef7c24413c804932ada upstream.
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). 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, this patch doesn't update the parent resource pointer in the case we have to wait for a muxed region right after.
Reported-and-tested-by: Vincent Pelletier <plr.vincent@gmail.com> Signed-off-by: Simon Guinot <simon.guinot@sequanux.org> Tested-by: Vincent Donnefort <vdonnefort@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- kernel/resource.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/kernel/resource.c +++ b/kernel/resource.c @@ -886,9 +886,10 @@ struct resource * __request_region(struc 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);
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