Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755243AbaKOB76 (ORCPT ); Fri, 14 Nov 2014 20:59:58 -0500 Received: from mail-vc0-f177.google.com ([209.85.220.177]:48937 "EHLO mail-vc0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755034AbaKOB75 (ORCPT ); Fri, 14 Nov 2014 20:59:57 -0500 MIME-Version: 1.0 In-Reply-To: References: <20141114213124.GB3344@redhat.com> Date: Fri, 14 Nov 2014 17:59:56 -0800 X-Google-Sender-Auth: _XiK3XtO-_5LJ4dwH2hqIgqx6mQ Message-ID: Subject: Re: frequent lockups in 3.18rc4 From: Linus Torvalds To: Thomas Gleixner Cc: Dave Jones , Linux Kernel , "the arch/x86 maintainers" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 14, 2014 at 2:55 PM, Thomas Gleixner wrote: > > This stale entry is not relevant here because the thing is stuck in > generic_exec_single(). That wasn't really my argument. The fact that "do_flush_tlb_all()" was left over on the stack frame implies that we're not doing the range-flush, and if it was some odd bug with a negative range or something like that (due to the fix in commit ce9ec37bddb6), I'd expect the lockup to be due to a hung do_kernel_range_flush() or something. But the range flushing never even happens. > So from smp_call_function_many() we end up via > smp_call_function_single() in generic_exec_single(). > > So the only ways to get stuck there are: > > csd_lock(csd); > and > csd_lock_wait(csd); Judging by the code disassembly, it's the "csd_lock_wait(csd)" at the end. The disassembly looks like 29: f3 90 pause 2b:* f6 43 18 01 testb $0x1,0x18(%rbx) <-- trapping instruction 2f: 75 f8 jne 0x29 31: 31 c0 xor %eax,%eax and that "xor %eax,%eax" seems to be part of the "return 0" immediately afterwards. But that's not entirely conclusive, it's just a strong hint. It does sound like there might be some IPI issue. I just don't see *any* changes in this area since 3.17. Some unrelated APIC change? I don't see that either. As you noted, there are KVM changes, but apparently that isn't involved either. Linus -- 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/