Messages in this thread | | | Date | Wed, 14 Sep 2005 15:26:10 -0700 (PDT) | Subject | Re: [PATCH 5/5] remove HAVE_ARCH_CMPXCHG | From | "David S. Miller" <> |
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From: Russell King <rmk+lkml@arm.linux.org.uk> Date: Wed, 14 Sep 2005 23:03:53 +0100
> What business has userspace got of telling whether cmpxchg works on > an architecture by looking at kernel headers?
Russell, please don't fly off the handle like this.
Nick is talking about something slightly different.
Things, for example, like DRM assume there is a cmpxchg() they can use in the kernel and userland for interlocking.
DRM doesn't actually _check_ anything to see if this is the case, it just so happens to only get enabled on platforms where cmpxchg() is available in this fashion.
What Nick is suggesting is to actually move HAVE_ARCH_CMPXCHG or something like it into the Kconfig so that things like DRM can actually do the correct dependency check. If you want something like "HAVE_ARCH_CMPXCHG_WHICH_CAN_INTERFACE_WITH_USERSPACE" that DRM can check too, all the better.
It's not about whether userspace can include some kernel header and get cmpxchg(), it's whether there is some way that a cmpxchg() shared semaphore between userspace and kernel is possible, which things like DRM depend upon having available. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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