Hi Edgar -- I'm just looking back at these signal handling race condition fix patches, and with this one I have a confusion about the Microblaze Linux syscall code that I hope you can clear up for me.
Looking at the kernel entry.S code it looks to me like the way syscalls work on microblaze is: * syscall insn is brki r14 * the insn itself saves the PC of the brki into r14 * on entry the kernel advances r14 by 4 to skip the brki * then SAVE_REGS saves r14 into the 'PC' slot in the pt_regs struct * for syscall restart handle_restart() may wind the PC value in the pt_regs back by 4 * in any case, on syscall exit we pull the PC value out of pt_regs into r14, and do a return with rtbd r14, 0 I think what this implies is that: * r14 is a "used by the kernel, may be corrupted at any time, not to be touched by userspace" register * on exit from a syscall PC and r14 are always the same * this includes do_sigreturn, ie "taking a signal" is one of the things that can corrupt r14 Is that right? (For context, the original patch is this one: http://patchwork.ozlabs.org/patch/514879/ and I now suspect my review comments at the time to be wrong.) thanks -- PMM