On 09/26, Oleg Nesterov wrote:
Thanks Peter.
Well. I'am afraid my testing was wrong, because Karel reports
it fixes the problem...
But. I applied this patch to my 3.11 tree (last commit is bff157b3a)
which also has the additional patch (03e12617 "tty: disassociate_ctty()
sends the extra SIGCONT"), and
TET_CONFIG=CFG TET_ROOT=. ./T.tcflush 4
still fails... T.tcflush was compiled on another (Karel's) machine,
perhaps there is something in libc, I do not know.
So let me ask just in case, I assume the fix below doesn't depend on
other changes I could miss?
I'll retest after git-pull and report...
Still fails under the Linus's tree + this patch.
However!!!
Tested-by: Oleg Nesterov <oleg@xxxxxxxxxx>
It turns out, T.tcflush doesn't expect it can start as a process group
leader. In this case setsid() fails, then tty_open() doesn't set
signal->tty, and thus this patch makes no difference: tty_check_change()
fails because tty doesn't match signal->tty.
And indeed, this test passes if you run it under strace, or simply do
$ TET_CONFIG=CFG TET_ROOT=. perl -e "system './T.tcflush 4'"
And damn, the fact it doesn't fail under strace doesn't allow you to
see that setsid() fails ;)
This is probably explains why Karel reported success, perhaps he
didn't run this test individually.
Thanks again Peter. Perhaps my analysis was wrong (and I do not see
setsid() in the sources), I do not really care. but perhaps tcflush.c
should be updated.