Malloc inside linux signal handler causes deadlock

Question

First of all, sorry to call malloc inside the signal handler :). I also understand that we should not do any laborious task / this kind of nasty stuff inside the signal handler.

But am I curious to know the reason why it crashed?

 #0  0x00006e3ff2b60dce in _lll_lock_wait_private () from /lib64/libc.so.6
 #1  0x00006e3ff2aec138 in _L_lock_9164 () from /lib64/libc.so.6
 #2  0x00006e3ff2ae9a32 in malloc () from /lib64/libc.so.6
 #3  0x00006e3ff1f691ad in ?? () from ..

I got a similar kernel specified at https://access.redhat.com/solutions/48701 .

Operating System: RHEL

Answer 1

malloc() , . . , malloc() . . man signal , .

GDB, , malloc() , malloc() , .

Answer 2

.

Per POSIX:

, [replicated below], . . , POSIX.1-2008 , , , (, exit(), to main()) , undefined. , longjmp().

" " , " undefined".

Linux signal.7 man page:

Async

,         -        . POSIX " ".         ,         ,        longjmp() siglongjmp(),         , undefined.

Linux , Linux. POSIX - , . " " POSIX " " :

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_exit()
abort()
accept()
access()
aio_error()
aio_return()
aio_suspend()
alarm()
bind()
cfgetispeed()
cfgetospeed()
cfsetispeed()
cfsetospeed()
chdir()
chmod()
chown()
clock_gettime()
close()
connect()
creat()
dup()
dup2()
execl()
execle()
execv()
execve()
faccessat()
fchdir()
fchmod()
fchmodat()
fchown()
fchownat()
fcntl()
fdatasync()
fexecve()
ffs()
fork()
fstat()
fstatat()
fsync()
ftruncate()
futimens()
getegid()
geteuid()
getgid()
getgroups()
getpeername()
getpgrp()
getpid()
getppid()
getsockname()
getsockopt()
getuid()
htonl()
htons()
kill()
link()
linkat()
listen()
longjmp()
lseek()
lstat()
memccpy()
memchr()
memcmp()
memcpy()
memmove()
memset()
mkdir()
mkdirat()
mkfifo()
mkfifoat()
mknod()
mknodat()
ntohl()
ntohs()
open()
openat()
pause()
pipe()
poll()
posix_trace_event()
pselect()
pthread_kill()
pthread_self()
pthread_sigmask()
raise()
read()
readlink()
readlinkat()
recv()
recvfrom()
recvmsg()
rename()
renameat()
rmdir()
select()
sem_post()
send()
sendmsg()
sendto()
setgid()
setpgid()
setsid()
setsockopt()
setuid()
shutdown()
sigaction()
sigaddset()
sigdelset()
sigemptyset()
sigfillset()
sigismember()
siglongjmp()
signal()
sigpause()
sigpending()
sigprocmask()
sigqueue()
sigset()
sigsuspend()
sleep()
sockatmark()
socket()
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stat()
stpcpy()
stpncpy()
strcat()
strchr()
strcmp()
strcpy()
strcspn()
strlen()
strncat()
strncmp()
strncpy()
strnlen()
strpbrk()
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strstr()
strtok_r()
symlink()
symlinkat()
tcdrain()
tcflow()
tcflush()
tcgetattr()
tcgetpgrp()
tcsendbreak()
tcsetattr()
tcsetpgrp()
time()
timer_getoverrun()
timer_gettime()
timer_settime()
times()
umask()
uname()
unlink()
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utime()
utimensat()
utimes()
wait()
waitpid()
wcpcpy()
wcpncpy()
wcscat()
wcschr()
wcscmp()
wcscpy()
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wcslen()
wcsncat()
wcsncmp()
wcsncpy()
wcsnlen()
wcspbrk()
wcsrchr()
wcsspn()
wcsstr()
wcstok()
wmemchr()
wmemcmp()
wmemcpy()
wmemmove()
wmemset()
write()

Answer 3

malloc glibc. , . malloc 'd , , malloc. malloc , , . . , AS-safe.

Answer 4

OP. glibc (, malloc arenas printf) concurrency. , "lll_", , .

: 1) 2) glibc - . . printf, write. glibc malloc, syscall (sbrk...) - , , ... 3) ,