On Thu, Aug 30, 2018 at 02:26:51PM +0800, Jia He wrote: > On 8/30/2018 9:00 AM, Jia He Wrote: > > On 8/30/2018 7:22 AM, Andrew Morton Wrote: > >> On Tue, 28 Aug 2018 12:20:46 +0800 Jia He <hejianet@xxxxxxxxx> wrote: > >>> FYI,I watched a lockdep warning based on your mmotm master branch[1] > >> > >> Thanks. We'll need help from ARM peeps on this please. > >> > >>> [ 6.692731] ------------[ cut here ]------------ > >>> [ 6.696391] DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled) [...] > >>> I thought the root cause might be at [2] which seems not in your branch yet. > >>> > >>> [1] http://git.cmpxchg.org/cgit.cgi/linux-mmotm.git > >>> [2] > >>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=efd112 > >> > >> I agree, that doesn't look like the culprit. But something may well > >> have gone wrong in "the recent conversion of the syscall entry/exit > >> code to C". > > Sorry for my unclearly previously description. > > 1. no such lockdep warning in latest mainline kernel git tree. > > 2. there is a 100% producible warning based on your latest mmotm tree > > 3. after applying the commit efd112 based on your mmotm tree, the warning > > disappearred > > > > I will do some further digging to answer your question if no other experts' help > > > 1. in el0_svc->el0_svc_common, without commit efd112 > local_daif_mask(); //disable the irq and trace irq off > flags = current_thread_info()->flags; > if (!has_syscall_work(flags)) > ------------ //1 > return; > If el0_svc_common enters the logic at line 1, the irq is disabled and > current->hardirqs_enabled is 0. > > 2. then it goes to el0_da > in el0_da, it enables the irq without changing current->hardirqs_enabled to 1 > > 3. goes to el0_da->do_mem_abort->... the lockdep warning happens > > The commit efd112 fixes it by invoking trace_hardirqs_off at line 1. > It closes the inconsistency window. Right, we fixed this last month in commit efd112353bf7 ("arm64: svc: Ensure hardirq tracing is updated before return"). Is there anything more you need from us on the Arm side? Will
