> On Dec 18, 2018, at 11:53 AM, Vineet Gupta <vineet.gup...@synopsys.com> wrote: > > Use on-stack smaller buffers instead of dynamic pages. > > The motivation for this change was to address lockdep splat when > signal handling code calls show_regs (with preemption disabled) and > ARC show_regs calls into sleepable page allocator. > > | potentially unexpected fatal signal 11. > | BUG: sleeping function called from invalid context at > ../mm/page_alloc.c:4317 > | in_atomic(): 1, irqs_disabled(): 0, pid: 57, name: segv > | no locks held by segv/57. > | Preemption disabled at: > | [<8182f17e>] get_signal+0x4a6/0x7c4 > | CPU: 0 PID: 57 Comm: segv Not tainted 4.17.0+ #23 > | > | Stack Trace: > | arc_unwind_core.constprop.1+0xd0/0xf4 > | __might_sleep+0x1f6/0x234 > | __get_free_pages+0x174/0xca0 > | show_regs+0x22/0x330 > | get_signal+0x4ac/0x7c4 # print_fatal_signals() -> preempt_disable() > | do_signal+0x30/0x224 > | resume_user_mode_begin+0x90/0xd8 > > Despite this, lockdep still barfs (see next change), but this patch > still has merit as in we use smaller/localized buffers now and there's > less instructoh trace to sift thru when debugging pesky issues. > > Signed-off-by: Vineet Gupta <vgu...@synopsys.com>
I would rather see 256 as a #define somewhere rather than a magic number sprinkled around arch/arc/kernel/troubleshoot.c. Still, that's what the existing code does, so I suppose it's OK. Otherwise the change looks good. Reviewed-by: William Kucharski <william.kuchar...@oracle.com>
