Re: [PATCH] arm64: reenable interrupt when handling ptrace breakpoint

On Mon, 21 Dec 2015, Will Deacon wrote:

+static void send_user_sigtrap(int si_code) +{

• struct pt_regs *regs = current_pt_regs();
• siginfo_t info = {

• .si_signo	= SIGTRAP,
  

• .si_errno	= 0,
  

• .si_code	= si_code,
  

• .si_addr	= (void __user *)instruction_pointer(regs),
  

• };
• if (WARN_ON(!user_mode(regs)))

• return;
  

• preempt_disable();

That doesn't work on RT either. force_sig_info() takes task->sighand->siglock, which is a 'sleeping' spinlock on RT.

Why would we need to disable preemption here at all? What's the problem of being preempted or even migrated?

Thanks,

tglx