On 01/10/2012 09:19 PM, Dmitry V. Levin wrote:
>> While at it, I made it so that we do display returned value/errno.
>> I see no point in hiding it and showing uninformative "= ?" instead.
>
> Is there any actual difference? Is there any case when sigreturn() may
> "return" something different from EINTR?
Yes. -EINTR return means that the interrupted system call won't be restarted.
It looks like this:
rt_sigsuspend([ABRT]) = ? ERESTARTNOHAND (To be restarted)
--- {si_signo=SIGALRM, si_code=SI_KERNEL, si_value={int=134513920,
ptr=0x8048500}} (Alarm clock) ---
alarm(1) = 0
sigreturn() (mask now [ABRT]) = -1 EINTR (Interrupted system call)
Whereas the case when syscall is restarted looks like this:
read(0, 0x8121750, 1024) = ? ERESTARTSYS (To be restarted)
--- {si_signo=SIGALRM, si_code=SI_KERNEL, si_value={int=134513920,
ptr=0x8048500}} (Alarm clock) ---
alarm(1) = 0
sigreturn() (mask now [ABRT]) = 3
read(0, 0x8121750, 1024)...
This is a potentially useful bit of information we weren't showing.
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