* Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote: > On Thu, Apr 15, 2010 at 08:49:40AM +0200, Ingo Molnar wrote: > > > > * Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> wrote: > > > > > Hi all, > > > > > > Yesterday's (and today's) linux-next boot (PowerPC) failed like this: > > > > > > ------------[ cut here ]------------ > > > Badness at kernel/lockdep.c:2301 > > > NIP: c0000000000a35c8 LR: c0000000000084c4 CTR: 0000000000000000 > > > REGS: c000000000bf77e0 TRAP: 0700 Not tainted (2.6.34-rc4-autokern1) > > > MSR: 8000000000021032 <ME,CE,IR,DR> CR: 24000044 XER: 00000004 > > > TASK = c000000000aa3d30[0] 'swapper' THREAD: c000000000bf4000 CPU: 0 > > > GPR00: 0000000000000001 c000000000bf7a60 c000000000bf32f0 c0000000000084c4 > > > GPR04: 0000000000000000 0000000000000a00 0000000000000000 0000000000000068 > > > GPR08: 0000000000000008 c000000000c4fabe 0000000000000000 7265677368657265 > > > GPR12: 8000000000009032 c000000007691000 0000000001c00000 c000000000770bf8 > > > GPR16: c00000000076f390 0000000000000000 0000000000430000 00000000024876f0 > > > GPR20: c000000000887480 0000000002487480 c0000000008876f0 0000000001b5f8d0 > > > GPR24: c000000000770478 0000000003300000 c000000000c1f1c8 c000000000884610 > > > GPR28: c000000000c1b290 c0000000000084c4 c000000000b45068 c000000000aa3d30 > > > NIP [c0000000000a35c8] .trace_hardirqs_on_caller+0xb0/0x224 > > > LR [c0000000000084c4] system_call_common+0xc4/0x114 > > > Call Trace: > > > [c000000000bf7a60] [c000000000bf7ba0] init_thread_union+0x3ba0/0x4000 (unreliable) > > > [c000000000bf7af0] [c0000000000084c4] system_call_common+0xc4/0x114 > > > --- Exception: c01 at .kernel_thread+0x28/0x70 > > > LR = .rest_init+0x34/0xf8 > > > [c000000000bf7de0] [c00000000086916c] .proc_sys_init+0x20/0x64 (unreliable) > > > [c000000000bf7e50] [c0000000000099c0] .rest_init+0x20/0xf8 > > > [c000000000bf7ee0] [c000000000848af0] .start_kernel+0x484/0x4a8 > > > [c000000000bf7f90] [c0000000000083c0] .start_here_common+0x1c/0x5c > > > Instruction dump: > > > 409e0188 0fe00000 48000180 801f08d8 2f800000 41be0050 880d01da 2fa00000 > > > 41be0028 e93e8538 88090000 68000001 <0b000000> 2fa00000 41be0010 e93e8538 > > > ------------[ cut here ]------------ > > > > > > Caused by commit bd6d29c25bb1a24a4c160ec5de43e0004e01f72b ("lockstat: > > > Make lockstat counting per cpu"). This added a WARN_ON_ONCE to > > > debug_atomic_inc() which is called from trace_hardirqs_on_caller() with > > > irqs enabled. > > > > > > Line 2301 is: > > > > > > if (unlikely(curr->hardirqs_enabled)) { > > > debug_atomic_inc(redundant_hardirqs_on); <--- 2301 > > > return; > > > } > > > > > > This is especially bad since on PowerPC, WARN_ON is a TRAP and the return > > > path from the TRAP also calls trace_hardirqs_on_caller(), so the TRAP > > > recurses ... > > > > Ok, we'll fix the warning. > > > > Btw., WARN_ON trapping on PowerPC is clearly a PowerPC bug - there's a good > > reason we have WARN_ON versus BUG_ON - it should be fixed. > > > In this case, I guess the following fix should be sufficient? > I'm going to test it and provide a sane changelog. > > > diff --git a/kernel/lockdep.c b/kernel/lockdep.c > index 78325f8..65d4336 100644 > --- a/kernel/lockdep.c > +++ b/kernel/lockdep.c > @@ -2298,7 +2298,11 @@ void trace_hardirqs_on_caller(unsigned long ip) > return; > > if (unlikely(curr->hardirqs_enabled)) { > + unsigned long flags; > + > + raw_local_irq_save(flags); > debug_atomic_inc(redundant_hardirqs_on); > + raw_local_irq_restore(flags); > return; > } > /* we'll do an OFF -> ON transition: */ that looks rather ugly. Why not do a raw: this_cpu_inc(lockdep_stats.redundant_hardirqs_on); which basically open-codes debug_atomic_inc(), but without the warning? Btw., using the this_cpu() methods might result in faster code for all the debug_atomic_inc() macros as well? Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html