Date: Wed, 1 Oct 2014 00:46:35 -0400 From: Ryan Stone <rysto32@gmail.com> To: Larry Baird <lab@gta.com> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: Kernel/Compiler bug Message-ID: <CAFMmRNxAYcr8eEY0SJsX3zkRadjT29-mfsGcSTmG_Yx-Hidi6w@mail.gmail.com> In-Reply-To: <20141001031553.GA14360@gta.com> References: <20141001031553.GA14360@gta.com>
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This may not be a compiler bug. A quick look at the esp values provided in that backtrace shows that at least 7KB has been used on the stack. The stack for kernel threads is only 8KB, and a stack overflow can cause a double fault like that. My suspicion would be that without optimizations on clang uses a lot more stack space and you push over the limit. There's a kernel build option for the stack size that you could change to confirm. I believe that it's called KSTACK_PAGES. Try increasing it to 4.
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