Re: Deadlock when receiving kill-signal from child process

[Mathias Fredriksson <mafredri@gmail.com>]

On Wed, Aug 5, 2015 at 11:20 PM, Bart Schaefer wrote:
}
} Dang.  Not sure there's much we can do about that one, that's the stdio
} library deadlocking internally on a mutex because a signal arrived.
} It'd be pretty ugly for us to try to wrap every stdio call with signal
} blocking.

Oh, interesting how this is only a problem on some systems.

}
} Yet another one of these.  We may have to resort to treating all signals
} the way we treat WINCH, that is, having them constantly queued except
} for specific moments when we unqueue them.

Ah, that explains why I have been able to work around this issue with WINCH.

}
} diff --git a/Src/parse.c b/Src/parse.c

Still locks up, interesting though is that this patch allows Ctrl+C to
exit the program even though it's frozen, the previous patch disabled
Ctrl+C, the one before that enabled Ctrl+C and before that it didn't
work either. Sorry for rambling, just trying to provide any additional
information I can.

forked child:

#0  0x00007fff8abf95da in syscall_thread_switch ()
#1  0x00007fff853a982d in _OSSpinLockLockSlow ()
#2  0x00007fff896e16d9 in szone_force_lock ()
#3  0x00007fff896e15e6 in _malloc_fork_prepare ()
#4  0x00007fff82cb8097 in fork ()
#5  0x000000010b9f6638 in zfork ()
#6  0x000000010b9fa0c5 in execcmd ()
#7  0x000000010b9f5128 in execpline ()
#8  0x000000010b9f46d2 in execlist ()
#9  0x000000010b9f44fa in execode ()
#10 0x000000010b9f80ff in runshfunc ()
#11 0x000000010b9f7bea in doshfunc ()
#12 0x000000010ba3c867 in dotrapargs ()
#13 0x000000010ba3b9ca in handletrap ()
#14 0x000000010ba3b2c8 in zhandler ()
#15 <signal handler called>
#16 0x00007fff896ddfc7 in small_free_list_add_ptr ()
#17 0x00007fff896d9ccf in szone_free_definite_size ()
#18 0x000000010ba2bc12 in bld_eprog ()
#19 0x000000010ba0cc3c in loop ()
#20 0x000000010ba0fa94 in zsh_main ()
#21 0x00007fff8610c5c9 in start ()

no fork:

#0  0x00007fff8abf95da in syscall_thread_switch ()
#1  0x00007fff853a982d in _OSSpinLockLockSlow ()
#2  0x00007fff896d98d6 in szone_free_definite_size ()
#3  0x000000010663c351 in freejob ()
#4  0x000000010663bd9d in printjob ()
#5  0x000000010663b0f2 in update_job ()
#6  0x0000000106665593 in wait_for_processes ()
#7  0x00000001066652be in zhandler ()
#8  <signal handler called>
#9  0x00007fff896d9e25 in szone_free_definite_size ()
#10 0x0000000106666885 in dotrapargs ()
#11 0x00000001066659ca in handletrap ()
#12 0x00000001066652c8 in zhandler ()
#13 0x000000010661fa29 in execpline ()
#14 0x000000010661e6d2 in execlist ()
#15 0x000000010661e4fa in execode ()
#16 0x0000000106636e43 in loop ()
#17 0x0000000106639a94 in zsh_main ()
#18 0x00007fff8610c5c9 in start ()