On Fri, Nov 14, 2014 at 2:55 PM, Thomas Gleixner <t...@linutronix.de> 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 majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/