[lkml]   [2018]   [Jul]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH v2 20/20] signal: Don't restart fork when signals come in.
Linus Torvalds <> writes:

> On Tue, Jul 24, 2018 at 1:40 PM Eric W. Biederman <> wrote:
>> + if (signal_pending(current)) {
>> + retval = restart_syscall();
>> + goto fork_out;
>> + }
> Oh, the previous version had this too, but it wasn't as obvious
> because it was just in a single line:
> return ERR_PTR(restart_syscall());
> but it's just crazy.
> It should just be
> if (signal_pending(current))
> goto fork_out;
> because it's just silly and pointless to change the code to use
> restart_syscall() here.
> All restart_syscall() does is
> set_tsk_thread_flag(current, TIF_SIGPENDING);
> and you just *checked* that TIF_SIGPENDING was already set. So the
> above is completely pointless.
> It is not clear why you made that change. The old code had the simpler
> "just return -ERESTARTNOINTR" model.
> Did the restart_syscall() thing come in by mistake from some previous
> trials and it just hung around?

I think this is the one place in the kernel where we can restart a
system call and not set TIF_SIGPENDING.

Several years ago I made the mistake in the networking code of returning
-ERESTARTNOINTR and forgetting to set TIF_SIGPENDING. That wasn't fun.
So I wrote restart_syscall and use it so I don't make that mistake

In this case your suggesting will definitely generate better code so I
am happy to make a V3 with that doesn't use restart_syscall. A person
working in the guts of fork can reasonably be expected understand and to
have all of the subtleties in cache as they work on that part of fork.


 \ /
  Last update: 2018-07-24 23:25    [W:0.105 / U:0.136 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site