Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 7 Mar 2016 12:03:18 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning |
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On Mon, 7 Mar 2016 11:41:37 -0500 (EST) Alan Stern <stern@rowland.harvard.edu> wrote:
> It's hard to call this a compiler bug, but perhaps it is -- I don't > know how programmers are supposed to tell CLANG that a subroutine > modifies the Interrupt Flag in a way that the compiler shouldn't mess > up.
Really! This is what's is happening??
Clang takes this:
if (!--hid->open) { spin_unlock_irq(X); do_something(); } else { spin_unlock_irq(X); }
Thus it's basically doing:
FLAG = !--hid->open; push flags; spin_unlock_irq(X) pop flags; if (FLAG zero set) { do_something(); }
OUCH!!! There's gotta be a way to turn that off, otherwise Clang can not be used to compile the kernel.
Nice detective work.
-- Steve
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