This is weird syzygy@lumby ~ $ grep DEBUG_FS /usr/src/linux/.config # CONFIG_DEBUG_FS is not set
But the entry in menuconfig ->kernel hacking looks like this:' -*- Debug Filesystem', and can't be changed. Not '[*]' which is changeable with the spacebar, but '-*-' which is not. According to <help> it depends on TREE_RCU_TRACE=y OR <a whole bunch of other stuff>. But I have TREE_RCU_TRACE=y. So I should be good right? But then why doesn't it select DEBUG_FS? googling lead me to http://en.wikipedia.org/wiki/Debugfs, which says do: 'mount -t debugfs none /sys/kernel/debug'. Ok, but there's no debug file or dir under /sys/kernel. Do I make one? And will it make a difference since according to grep DEBUG_FS is not set in the kernel config? I'll go and make the new kernel and see what happens. On 6/30/12, Maxim Wexler <maxim.wex...@gmail.com> wrote: >> Hi, >> >> I don't have an answer, but if you google the phrase "rcu_bh detected >> stall on CPU" you can find many reports similar to yours and maybe >> some information. > > This might be usefu > lhttp://www.kernel.org/doc/Documentation/RCU/stallwarn.txt > > "RCU bugs can often be debugged with the help of CONFIG_RCU_TRACE" > > from <help> in menuconfig. > > │ This option provides tracing in RCU which presents stats > │ > │ in debugfs for debugging RCU implementation. > > Ok, so I've set the RCU_TRACE=y. Next question: How do I use debugfs, > never used it before? > >> >> Do you have RCU_CPU_STALL_INFO=y in your kernel config? > > no. > > syzygy@lumby ~ $ grep RCU /usr/src/linux/.config > # RCU Subsystem > CONFIG_TREE_RCU=y > # CONFIG_PREEMPT_RCU is not set > # CONFIG_RCU_TRACE is not set > CONFIG_RCU_FANOUT=32 > # CONFIG_RCU_FANOUT_EXACT is not set > # CONFIG_RCU_FAST_NO_HZ is not set > # CONFIG_TREE_RCU_TRACE is not set > # CONFIG_SPARSE_RCU_POINTER is not set > CONFIG_RCU_CPU_STALL_TIMEOUT=60 >
