Hi Russell, Russell King - ARM Linux <li...@arm.linux.org.uk> wrote on 09/02/2011 07:48:12 PM:
> On Fri, Sep 02, 2011 at 07:40:34PM +0200, Ulrich Weigand wrote: > > Russell King - ARM Linux <li...@arm.linux.org.uk> wrote on 09/02/2011 > > 07:22:59 PM: > > > On Fri, Sep 02, 2011 at 04:47:35PM +0200, Ulrich Weigand wrote: > > > > Assume the scenario you initally describe, where a first signal is > > > > ignored and leads to system call restart. With your latest patch, > > > > you call into syscall_restart which sets everything up to restart > > > > the call (with interrupts disabled). > > > > > > I don't think SIG_IGN signals even set the TIF work flag, so they > > > never even cause a call into do_signal(). Therefore, as far as > > > syscalls go, attempting to send a process (eg) a SIGINT which its > > > handler is set to SIG_IGN results in the process not even being > > > notified about the attempt - we won't even wake up while the > > > syscall is sleeping. > > > > I don't see why SIG_IGN signals shouldn't set the TIF work flag; > > the decision whether to ignore a signal is only made once we've > > got to get_signal_to_deliver. > > Yes, having looked deeper, you seem to be right - but only if the thread > is being ptraced. If it's not being ptraced, ignored signals don't > make it that far. > > And yes, we can end up processing the interrupt before the SVC is > executed, which is still a hole. So we need to avoid doing the > restart in userspace - which might actually make things easier. > I'll take a look into that over the weekend. After some more discussions with Uli I've now created a patch that hopefully will address the issue on s390. The new code always uses the TIF_RESTART_SVC work flag to restart the system call if there is no signal to deliver. Only if there is a signal to deliver the traditional rewind of the instruction pointer is used to restart the system call (for -ERESTARTNOINTR and -ERESTARTSYS with a SA_RESTART signal handler). In case you are interested in the code is available at git://git390.marist.edu/pub/scm/linux-2.6.git features in particular git commit 4a6a001c39ac196530d8378408b61d6d2fee70d9. blue skies, Martin _______________________________________________ linaro-toolchain mailing list linaro-toolchain@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-toolchain
