Bug#794063: background process reading from terminal makes processes hang
Hello,
when logging system calls with strace on the process that created the
control socket the following can be seen (when the 2nd ssh on the same
terminal is started):
[select(12, [3 4 8 9], [], NULL, {15, 0}]
) = 1 (in [4], left {11, 431772})
clock_gettime(CLOCK_BOOTTIME, {12450, 924219877}) = 0
accept(4, {sa_family=AF_LOCAL, NULL}, [2]) = 5
getsockopt(5, SOL_SOCKET, SO_PEERCRED, {pid=26544, uid=1000, gid=1000}, [12]) = 0
getuid() = 1000
fcntl(5, F_SETFD, FD_CLOEXEC) = 0
fcntl(5, F_GETFL) = 0x2 (flags O_RDWR)
fcntl(5, F_SETFL, O_RDWR|O_NONBLOCK) = 0
fcntl(5, F_GETFL) = 0x802 (flags O_RDWR|O_NONBLOCK)
clock_gettime(CLOCK_BOOTTIME, {12450, 924749258}) = 0
clock_gettime(CLOCK_BOOTTIME, {12450, 924807734}) = 0
select(12, [3 4 5 8 9], [5], NULL, {15, 0}) = 2 (in [5], out [5], left {14, 999994})
clock_gettime(CLOCK_BOOTTIME, {12450, 924941979}) = 0
read(5, "\0\0\0\10", 4) = 4
read(5, "\0\0\0\1\0\0\0\4", 8) = 8
write(5, "\0\0\0\10\0\0\0\1\0\0\0\4", 12) = 12
clock_gettime(CLOCK_BOOTTIME, {12450, 925180653}) = 0
clock_gettime(CLOCK_BOOTTIME, {12450, 925235379}) = 0
select(12, [3 4 5 8 9], [], NULL, {15, 0}) = 1 (in [5], left {14, 999994})
clock_gettime(CLOCK_BOOTTIME, {12450, 925360439}) = 0
read(5, "\0\0\0\10", 4) = 4
read(5, "\20\0\0\4\0\0\0\0", 8) = 8
clock_gettime(CLOCK_BOOTTIME, {12450, 925536700}) = 0
clock_gettime(CLOCK_BOOTTIME, {12450, 925590213}) = 0
select(12, [3 4 5 8 9], [5], NULL, {15, 0}) = 1 (out [5], left {14, 999995})
clock_gettime(CLOCK_BOOTTIME, {12450, 925717764}) = 0
write(5, "\0\0\0\f\200\0\0\5\0\0\0\0\0\0ga", 16) = 16
clock_gettime(CLOCK_BOOTTIME, {12450, 925832117}) = 0
clock_gettime(CLOCK_BOOTTIME, {12450, 925885997}) = 0
select(12, [3 4 5 8 9], [], NULL, {15, 0}) = 1 (in [5], left {14, 999995})
clock_gettime(CLOCK_BOOTTIME, {12450, 926010243}) = 0
read(5, "\0\0\0@", 4) = 4
read(5, "\20\0\0\2\0\0\0\1\0\0\0\0\0\0\0\1\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0~"..., 64) = 64
recvmsg(5, {msg_name(0)=NULL, msg_iov(1)=[{"\0", 1}], msg_controllen=24, {cmsg_len=20, cmsg_level=SOL_SOCKET, cmsg_type=SCM_RIGHTS, {6}}, msg_flags=0}, 0) = 1
recvmsg(5, {msg_name(0)=NULL, msg_iov(1)=[{"\0", 1}], msg_controllen=24, {cmsg_len=20, cmsg_level=SOL_SOCKET, cmsg_type=SCM_RIGHTS, {7}}, msg_flags=0}, 0) = 1
recvmsg(5, {msg_name(0)=NULL, msg_iov(1)=[{"\0", 1}], msg_controllen=24, {cmsg_len=20, cmsg_level=SOL_SOCKET, cmsg_type=SCM_RIGHTS, {12}}, msg_flags=0}, 0) = 1
ioctl(6, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
ioctl(6, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
ioctl(7, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
ioctl(12, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
fcntl(6, F_SETFD, FD_CLOEXEC) = 0
fcntl(7, F_SETFD, FD_CLOEXEC) = 0
fcntl(12, F_SETFD, FD_CLOEXEC) = 0
clock_gettime(CLOCK_BOOTTIME, {12450, 926826653}) = 0
clock_gettime(CLOCK_BOOTTIME, {12450, 926905547}) = 0
select(13, [3 4 8 9], [3], NULL, {15, 0}) = 1 (out [3], left {14, 999995})
clock_gettime(CLOCK_BOOTTIME, {12450, 927034328}) = 0
write(3, "\0\0\0 \276\263|\344\300\250\304\25\330\325F\2076hL\t\4\241B`\217\271`\357\376\255N\311"..., 44) = 44
clock_gettime(CLOCK_BOOTTIME, {12450, 927205118}) = 0
clock_gettime(CLOCK_BOOTTIME, {12450, 927270057}) = 0
select(13, [3 4 8 9], [], NULL, {15, 0}) = 1 (in [3], left {14, 999995})
clock_gettime(CLOCK_BOOTTIME, {12450, 927408029}) = 0
read(3, "\0\0\0 \357\333\222yS\305js\305\372\273wc\242\32\355A\210\310\315\305\315EHE\306\35\261"..., 8192) = 44
ioctl(6, TIOCGWINSZ, {ws_row=24, ws_col=80, ws_xpixel=0, ws_ypixel=0}) = 0
clock_gettime(CLOCK_BOOTTIME, {12450, 927644303}) = 0
clock_gettime(CLOCK_BOOTTIME, {12450, 927700923}) = 0
select(13, [3 4 5 8 9], [3 5], NULL, {15, 0}) = 2 (out [3 5], left {14, 999994})
clock_gettime(CLOCK_BOOTTIME, {12450, 927830272}) = 0
write(5, "\0\0\0\f\200\0\0\6\0\0\0\1\0\0\0\4", 16) = 16
write(3, "\0\0\1@\372\241\227{\232\247F\"\211!\364\273\373\265p\272\346\245K\320\325\262Ey\10\322\315\375"..., 436) = 436
clock_gettime(CLOCK_BOOTTIME, {12450, 928059300}) = 0
clock_gettime(CLOCK_BOOTTIME, {12450, 928120850}) = 0
select(13, [3 4 5 8 9], [], NULL, {15, 0}) = 1 (in [3], left {14, 998954})
clock_gettime(CLOCK_BOOTTIME, {12450, 929408518}) = 0
read(3, "\0\0\0\20\372\347jh\242I\33\233\214\275\261}&4\274\300\207\2209\216\347CD\320\0\0\0\20"..., 8192) = 176
clock_gettime(CLOCK_BOOTTIME, {12450, 929613655}) = 0
clock_gettime(CLOCK_BOOTTIME, {12450, 929675983}) = 0
select(13, [3 4 5 6 8 9], [7], NULL, {15, 0}) = 1 (out [7], left {14, 999991})
clock_gettime(CLOCK_BOOTTIME, {12450, 929828373}) = 0
write(7, "Last login: Thu Jul 30 11:03:05 "..., 54) = 54
clock_gettime(CLOCK_BOOTTIME, {12450, 929950095}) = 0
clock_gettime(CLOCK_BOOTTIME, {12450, 930005636}) = 0
select(13, [3 4 5 6 8 9], [], NULL, {15, 0}) = 1 (in [3], left {14, 727921})
clock_gettime(CLOCK_BOOTTIME, {12451, 202284805}) = 0
read(3, "\0\0\0000\353\245\246uri\357m\220>\210\244\304\313\354\327R\3535\320\266d\202^:i\221\371"..., 8192) = 60
clock_gettime(CLOCK_BOOTTIME, {12451, 202472937}) = 0
clock_gettime(CLOCK_BOOTTIME, {12451, 202540369}) = 0
select(13, [3 4 5 6 8 9], [7], NULL, {15, 0}) = 1 (out [7], left {14, 999992})
clock_gettime(CLOCK_BOOTTIME, {12451, 202688970}) = 0
write(7, "\33]0;uwe@perseus: ~\7uwe@perseus:~"..., 34) = 34
clock_gettime(CLOCK_BOOTTIME, {12451, 202811407}) = 0
clock_gettime(CLOCK_BOOTTIME, {12451, 202882596}) = 0
select(13, [3 4 5 6 8 9], [], NULL, {15, 0}) = 1 (in [6], left {13, 639311})
clock_gettime(CLOCK_BOOTTIME, {12452, 563761064}) = 0
read(6, 0x7ffdc9f16de0, 16384) = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
--- SIGTTIN {si_signo=SIGTTIN, si_code=SI_KERNEL} ---
--- stopped by SIGTTIN ---
with fd 6 being the terminal of the process (that is also connected to file
descriptors 0 1 and 2).
Best regards
Uwe
Reply to: