Messages in this thread | | | Date | Thu, 28 Sep 2017 09:30:48 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH v3 tip/core/rcu 40/40] rcu: Make non-preemptive schedule be Tasks RCU quiescent state |
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On Thu, Sep 28, 2017 at 06:18:50PM +0200, Peter Zijlstra wrote: > On Thu, Sep 28, 2017 at 09:05:14AM -0700, Paul E. McKenney wrote: > > > do_async_page_fault+0x72/0x90 arch/x86/kernel/kvm.c:271 > > > async_page_fault+0x22/0x30 arch/x86/entry/entry_64.S:1069 > > > RIP: 0010:format_decode+0x240/0x830 lib/vsprintf.c:1996 > > > RSP: 0018:ffff88003b2df520 EFLAGS: 00010283 > > > RAX: 000000000000003f RBX: ffffffffb5d1e141 RCX: ffff88003b2df670 > > > RDX: 0000000000000001 RSI: dffffc0000000000 RDI: ffffffffb5d1e140 > > > RBP: ffff88003b2df560 R08: dffffc0000000000 R09: 0000000000000000 > > > R10: ffff88003b2df718 R11: 0000000000000000 R12: ffff88003b2df5d8 > > > R13: 0000000000000064 R14: ffffffffb5d1e140 R15: 0000000000000000 > > > vsnprintf+0x173/0x1700 lib/vsprintf.c:2136 > > > > We took a page fault in vsnprintf() while doing link_path_walk(), > > which looks to be within an RCU read-side critical section. > > > > Maybe the page fault confused lockdep? > > > > Sigh. It is going to be a real pain if all printk()s need to be > > outside of RCU read-side critical sections due to the possibility of > > page faults... > > printk() _should_ not fault AFAIK. If it does, you've done something > dodgy.
And we really do have a page fault there. Perhaps the fault of the caller of printk(), printing some memory that is, as you say, dodgy?
Thanx, Paul
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