Re: [Qemu-devel] [PULL v4 00/35] Misc patches for 2018-12-21

[Peter Maydell]

On Fri, 4 Jan 2019 at 07:59, Paolo Bonzini <address@hidden> wrote:
> I don't know... I tried running make check under "strace -e fcntl" and I
> didn't find any occurrences of fcntl(1, O_SETFL, ...|O_NONBLOCK).

I found this strace command worked to track down some possible
culprits:
strace -o /tmp/strace.log -e fcntl,execve,clone -e signal=none -f make
-C build/x86 V=1 check

Extracts from the logs:

29251 execve("tests/test-char", ["tests/test-char", "-q", "-p",
"/char/stdio/subprocess", "--GTestSubprocess", "--GTestLogFD", "4"],
[/* 66 vars */] <unfinished ...>
29251 <... execve resumed> )            = 0
29251 fcntl(3, F_GETFD)                 = 0
29251 fcntl(3, F_SETFD, FD_CLOEXEC)     = 0
29251 clone(child_stack=0x7f43946addf0,
flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID,
parent_tidptr=0x7f43946ae9d0, tls=0x7f43946ae700,
child_tidptr=0x7f43946ae9d0) = 29254
29251 fcntl(4, F_GETFD)                 = 0
29251 fcntl(4, F_SETFD, FD_CLOEXEC)     = 0
29251 fcntl(4, F_GETFL)                 = 0x2 (flags O_RDWR)
29251 fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0
29251 fcntl(0, F_GETFL)                 = 0x8000 (flags O_RDONLY|O_LARGEFILE)
29251 fcntl(0, F_GETFL)                 = 0x8000 (flags O_RDONLY|O_LARGEFILE)
29251 fcntl(0, F_SETFL, O_RDONLY|O_NONBLOCK|O_LARGEFILE) = 0
29251 fcntl(1, F_GETFL)                 = 0x1 (flags O_WRONLY)
29251 fcntl(1, F_SETFL, O_WRONLY|O_NONBLOCK) = 0
29251 fcntl(0, F_SETFL, O_RDONLY|O_LARGEFILE) = 0
29251 fcntl(0, F_SETFL, O_RDONLY|O_LARGEFILE) = -1 EBADF (Bad file descriptor)
29254 +++ exited with 0 +++
29251 +++ exited with 0 +++

(the attempt to F_SETFL a closed stdin is also interesting).

and

30300 execve("tests/hexloader-test", ["tests/hexloader-test",
"--quiet", "--keep-going", "-m
=quick", "--GTestLogFD=6"], [/* 68 vars */]) = 0
30300 fcntl(3, F_GETFD)                 = 0
30300 fcntl(3, F_SETFD, FD_CLOEXEC)     = 0
30300 fcntl(4, F_GETFD)                 = 0
30300 fcntl(4, F_SETFD, FD_CLOEXEC)     = 0
30300 clone(child_stack=0,
flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD,
child_tidptr=0x7f26bdc09a10) = 30301
30301 execve("/bin/sh", ["sh", "-c", "exec
arm-softmmu/qemu-system-arm"...], [/* 69 vars */]) = 0
30301 execve("arm-softmmu/qemu-system-arm",
["arm-softmmu/qemu-system-arm", "-qtest",
"unix:/tmp/qtest-30300.sock,nowai"..., "-qtest-log", "/dev/null",
"-chardev", "socket,path=/tmp/qtest-30300.qmp"..., "-mon",
"chardev=char0,mode=control", "-machine", "accel=qtest", "-display",
"none", "-M", "vexpress-a9", "-nographic", ...], [/* 69 vars */]) = 0
30301 fcntl(3, F_GETFD)                 = 0
30301 fcntl(3, F_SETFD, FD_CLOEXEC)     = 0
30301 clone(child_stack=0x7f84f7614730,
flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID,
parent_tidptr=0x7f84f76179d0, tls=0x7f84f7617700,
child_tidptr=0x7f84f76179d0) = 30302
30301 fcntl(7, F_GETFD)                 = 0
30301 fcntl(7, F_SETFD, FD_CLOEXEC)     = 0
30301 fcntl(7, F_GETFL)                 = 0x2 (flags O_RDWR)
30301 fcntl(7, F_SETFL, O_RDWR|O_NONBLOCK) = 0
30301 fcntl(11, F_GETFL)                = 0x2 (flags O_RDWR)
30301 fcntl(11, F_SETFL, O_RDWR|O_NONBLOCK) = 0
30301 fcntl(12, F_GETFL)                = 0x2 (flags O_RDWR)
30301 fcntl(12, F_SETFL, O_RDWR|O_NONBLOCK) = 0
30301 clone(child_stack=0x7f84f6e13730,
flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID,
parent_tidptr=0x7f84f6e169d0, tls=0x7f84f6e16700,
child_tidptr=0x7f84f6e169d0) = 30303
30301 fcntl(0, F_GETFL)                 = 0x8000 (flags O_RDONLY|O_LARGEFILE)
30301 fcntl(0, F_GETFL)                 = 0x8000 (flags O_RDONLY|O_LARGEFILE)
30301 fcntl(0, F_SETFL, O_RDONLY|O_NONBLOCK|O_LARGEFILE) = 0
30301 fcntl(1, F_GETFL)                 = 0x8402 (flags
O_RDWR|O_APPEND|O_LARGEFILE)
30301 fcntl(1, F_SETFL, O_RDWR|O_APPEND|O_NONBLOCK|O_LARGEFILE) = 0
30301 clone(child_stack=0x7f84f6612730,
flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID,
parent_tidptr=0x7f84f66159d0, tls=0x7f84f6615700,
child_tidptr=0x7f84f66159d0) = 30304
30303 +++ exited with 0 +++
30301 fcntl(0, F_SETFL, O_RDONLY|O_LARGEFILE) = 0
30301 fcntl(0, F_SETFL, O_RDONLY|O_LARGEFILE) = -1 EBADF (Bad file descriptor)
30302 +++ exited with 0 +++
30301 +++ exited with 0 +++

where tests/hexloader-test starts a QEMU process which
makes stdin/stdout non-blocking.

I didn't try to also track dup/dup2/dup3 use to see whether fd 0/1/2
were duped to other fds and then set O_NONBLOCK via those, or
open to see if they were reopened with other contents.

(Test run is still in-progress, I'll update if there are any more
interesting bits of logging.)

thanks
-- PMM