The idea comes from the upstream discussion between Linus and Andrea: https://lore.kernel.org/lkml/20171102193644.GB22686@xxxxxxxxxx/ A summary to the issue: there was a special path in handle_userfault() in the past that we'll return a VM_FAULT_NOPAGE when we detected non-fatal signals when waiting for userfault handling. We did that by reacquiring the mmap_sem before returning. However that brings a risk in that the vmas might have changed when we retake the mmap_sem and even we could be holding an invalid vma structure. This patch is a preparation of removing that special path by allowing the page fault to return even faster if we were interrupted by a non-fatal signal during a user-mode page fault handling routine. Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Suggested-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> Signed-off-by: Peter Xu <peterx@xxxxxxxxxx> --- include/linux/sched/signal.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h index 4c87ffce64d1..09d40ce6a162 100644 --- a/include/linux/sched/signal.h +++ b/include/linux/sched/signal.h @@ -379,7 +379,8 @@ static inline bool fault_signal_pending(unsigned int fault_flags, struct pt_regs *regs) { return unlikely((fault_flags & VM_FAULT_RETRY) && - fatal_signal_pending(current)); + (fatal_signal_pending(current) || + (user_mode(regs) && signal_pending(current)))); } /* -- 2.24.1
