Just an FYI -- I'm delaying a new release that I had hoped to do today because backtraces for blocked x86_64 tasks no longer work with recent kernels because this commit removed the "thread_return" label: commit c12a229bc5971534537a7d0e49e44f9f1f5d0336 Author: Masami Hiramatsu <mhiramat(a)redhat.com&gt; Date: Thu Nov 5 11:03:59 2009 -0500 x86: Remove unused thread_return label from switch_to() Remove unused thread_return label from switch_to() macro on x86-64. Since this symbol cuts into schedule(), backtrace at the latter half of schedule() was always shown as thread_return(). Signed-off-by: Masami Hiramatsu <mhiramat(a)redhat.com&gt; Cc: systemtap <systemtap(a)sources.redhat.com&gt; Cc: DLE <dle-develop(a)lists.sourceforge.net&gt; LKML-Reference: <20091105160359.5181.26225.stgit@harusame> Signed-off-by: Ingo Molnar <mingo(a)elte.hu&gt; diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h index f08f973..1a953e2 100644 --- a/arch/x86/include/asm/system.h +++ b/arch/x86/include/asm/system.h @@ -128,8 +128,6 @@ do { \ "movq %%rsp,%P[threadrsp](%[prev])\n\t" /* save RSP */ \ "movq %P[threadrsp](%[next]),%%rsp\n\t" /* restore RSP */ \ "call __switch_to\n\t" \ - ".globl thread_return\n" \ - "thread_return:\n\t" \ "movq "__percpu_arg([current_task])",%%rsi\n\t" \ __switch_canary \ "movq %P[thread_info](%%rsi),%%r8\n\t" \ I've got a fix for x86_64 -- which have always depended on the existence of the "thread_return" label. But I note that x86 backtraces also are not working, which I'll take a look at today. Dave