Hi Paul, On 3.4.0-rc4-next-20120427 and preceding linux-nexts (I've not tried rc5-next-20120430 but expect it's the same), on PowerPC G5 quad with CONFIG_PREEMPT=y and CONFIG_DEBUG_ATOMIC_SLEEP=y, I'm getting spurious "BUG: sleeping function called from invalid context" messages from __might_sleep().
Just once I saw such a message during startup. Once I saw such a message when rebuilding the machine's kernel. Usually I see them when I'm running a swapping load of kernel builds under memory pressure (but that's what I'm habitually running there): perhaps after a few minutes a flurry comes, then goes away, comes back again later, and after perhaps a couple of hours of that I see "INFO: rcu_preempt detected stalls" messages too, and soon it freezes (or perhaps it's still running, but I'm so flooded by messages that I reboot anyway). Rather like from before you fixed schedule_tail() for your per-cpu RCU mods, but not so easy to reproduce. I did a bisection and indeed it converged as expected on the RCU changes. No such problem seen on x86: it looks as if there's some further tweak required on PowerPC. Here are my RCU config options (I don't usually have the TORTURE_TEST in, but tried that for half an hour this morning, in the hope that it would generate the issue: but it did not). # RCU Subsystem CONFIG_TREE_PREEMPT_RCU=y CONFIG_PREEMPT_RCU=y CONFIG_RCU_FANOUT=64 # CONFIG_RCU_FANOUT_EXACT is not set CONFIG_TREE_RCU_TRACE=y # CONFIG_RCU_BOOST is not set CONFIG_HAVE_RCU_TABLE_FREE=y # CONFIG_SPARSE_RCU_POINTER is not set CONFIG_RCU_TORTURE_TEST=m CONFIG_RCU_CPU_STALL_TIMEOUT=60 # CONFIG_RCU_CPU_STALL_VERBOSE is not set # CONFIG_RCU_CPU_STALL_INFO is not set CONFIG_RCU_TRACE=y Here's the message when I was rebuilding the G5's kernel: BUG: sleeping function called from invalid context at include/linux/pagemap.h:354 in_atomic(): 0, irqs_disabled(): 0, pid: 6886, name: cc1 Call Trace: [c0000001a99f78e0] [c00000000000f34c] .show_stack+0x6c/0x16c (unreliable) [c0000001a99f7990] [c000000000077b40] .__might_sleep+0x11c/0x134 [c0000001a99f7a10] [c0000000000c6228] .filemap_fault+0x1fc/0x494 [c0000001a99f7af0] [c0000000000e7c9c] .__do_fault+0x120/0x684 [c0000001a99f7c00] [c000000000025790] .do_page_fault+0x458/0x664 [c0000001a99f7e30] [c000000000005868] handle_page_fault+0x10/0x30 I've plenty more examples, most of them from page faults or from kswapd; but I don't think there's any more useful information in them. Anything I can try later on? Thanks! Hugh _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
