From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Wed, 07 Mar 2001 16:53:43 +0000 Subject: Re: [Linux-ia64] CONFIG_IA64_NEW_UNWIND Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Tue, 6 Mar 2001 16:48:07 -0800, "Luck, Tony" said: Tony> I'm running 2.4.0 with a couple of patches on 2-CPU Bigsur. I Tony> have a problem where a cpu apparently hangs when a process Tony> dumps core. The "hang" is caused when do_copy_regs() in Tony> arch/ia64/kernel/process.c picks up random values for RSE Tony> backing store addresses, and sits in this loop: Tony> for (addr = pt->ar_bspstore; addr < ar_bsp; addr += 8) Tony> if (ia64_peek(pt, current, addr, &val) = 0) Tony> access_process_vm(current, addr, &val, sizeof(val), 1); Tony> for a really long time (last time I caught it "addr" was Tony> 0x000003e2_47fbf540 and "ar_bsp" was 0x00006000_00000000 Tony> ... every call to ia64_peek() failed with EIO ... but I Tony> calculated that it would have taken over six weeks to complete Tony> the loop). That's a sign that the unwind info is incorrect. Are you by chance trying to use the 3.0 branch of gcc? There is a known bug in that compiler that's causing this problem. Tony> Looking back at where do_copy_regs() digs these values out of Tony> the stack, I think that the problem lies in these lines: Tony> unw_get_sp(info, &sp); pt = (struct pt_regs *) (sp + Tony> 16); Tony> We pick up a perfectly reasonable "sp" in the first line, but Tony> I can't see why the code believes that that there would be a Tony> pt_regs structure 16 bytes further up. I think that the frame Tony> looks like this at this point You missed the call to unw_unwind_to_user(). It rewinds the stack to the pt-regs structure created on entry to the kernel. --david