>env - PERL_SIGNALS=unsafe strace -o trace.txt /usr/bin/perl interrupted.pl
Sun May 24 20:51:14 2015 pid=32083: helper starts
Sun May 24 20:51:14 2015 pid=32082: main starts
Sun May 24 20:51:14 2015 pid=32082: main waiting for helper to lock
Sun May 24 20:51:15 2015 pid=32082: main flock
SIGALRM in main at interrupted.pl line 16.
Sun May 24 20:51:24 2015 pid=32083: helper ends
Sun May 24 20:51:24 2015 pid=32082: main flock done
Sun May 24 20:51:24 2015 pid=32082: main ends

>grep -C5 SIGALRM trace.txt
close(3)                                = 0
rt_sigprocmask(SIG_SETMASK, ~[RTMIN RT_1], [], 8) = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7fdbc5fc2a10) = 32083
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [ALRM], [], 8) = 0
rt_sigaction(SIGALRM, {0x7fdbc5ad9de0, [], SA_RESTORER|SA_RESTART, 0x7fdbc4ccb670}, {SIG_DFL, [], 0}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
open("/etc/localtime", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=2335, ...}) = 0
fstat(3, {st_mode=S_IFREG|0644, st_size=2335, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fdbc5fe6000
--
fcntl(3, F_SETFD, FD_CLOEXEC)           = 0
alarm(5)                                = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2335, ...}) = 0
write(1, "Sun May 24 20:51:15 2015 pid=320"..., 47) = 47
flock(3, LOCK_EX)                       = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
--- SIGALRM {si_signo=SIGALRM, si_code=SI_KERNEL} ---
rt_sigaction(SIGALRM, NULL, {0x7fdbc5ad9de0, [], SA_RESTORER|SA_RESTART, 0x7fdbc4ccb670}, 8) = 0
write(2, "SIGALRM in main at interrupted.p"..., 43) = 43
rt_sigreturn()                          = 73
flock(3, LOCK_EX)                       = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2335, ...}) = 0
write(1, "Sun May 24 20:51:24 2015 pid=320"..., 52) = 52
alarm(0)                                = 0
--
rt_sigaction(SIGKILL, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGUSR1, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGSEGV, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGUSR2, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGPIPE, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGALRM, NULL, {0x7fdbc5ad9de0, [], SA_RESTORER|SA_RESTART, 0x7fdbc4ccb670}, 8) = 0
rt_sigaction(SIGALRM, {SIG_DFL, [], SA_RESTORER|SA_RESTART, 0x7fdbc4ccb670}, {0x7fdbc5ad9de0, [], SA_RESTORER|SA_RESTART, 0x7fdbc4ccb670}, 8) = 0
rt_sigaction(SIGTERM, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGSTKFLT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGCONT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGSTOP, NULL, {SIG_DFL, [], 0}, 8) = 0

>env - strace -o trace.txt /usr/bin/perl interrupted.pl
Sun May 24 20:51:35 2015 pid=32103: helper starts
Sun May 24 20:51:35 2015 pid=32102: main starts
Sun May 24 20:51:35 2015 pid=32102: main waiting for helper to lock
Sun May 24 20:51:36 2015 pid=32102: main flock
SIGALRM in main at interrupted.pl line 16.
Sun May 24 20:51:41 2015 pid=32102: main can't lock: Interrupted system call (error code 4)
Sun May 24 20:51:41 2015 pid=32102: main flock done
Sun May 24 20:51:41 2015 pid=32102: main ends
Sun May 24 20:51:45 2015 pid=32103: helper ends

>grep -C5 SIGALRM trace.txt
close(3)                                = 0
rt_sigprocmask(SIG_SETMASK, ~[RTMIN RT_1], [], 8) = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f45f31f1a10) = 32103
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [ALRM], [], 8) = 0
rt_sigaction(SIGALRM, {0x7f45f2d08de0, [], SA_RESTORER, 0x7f45f1efa670}, {SIG_DFL, [], 0}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
open("/etc/localtime", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=2335, ...}) = 0
fstat(3, {st_mode=S_IFREG|0644, st_size=2335, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f45f3215000
--
fcntl(3, F_SETFD, FD_CLOEXEC)           = 0
alarm(5)                                = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2335, ...}) = 0
write(1, "Sun May 24 20:51:36 2015 pid=321"..., 47) = 47
flock(3, LOCK_EX)                       = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
--- SIGALRM {si_signo=SIGALRM, si_code=SI_KERNEL} ---
rt_sigreturn()                          = -1 EINTR (Interrupted system call)
rt_sigprocmask(SIG_BLOCK, [ALRM], [], 8) = 0
rt_sigaction(SIGALRM, NULL, {0x7f45f2d08de0, [], SA_RESTORER, 0x7f45f1efa670}, 8) = 0
write(2, "SIGALRM in main at interrupted.p"..., 43) = 43
rt_sigprocmask(SIG_UNBLOCK, [ALRM], NULL, 8) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2335, ...}) = 0
write(1, "Sun May 24 20:51:41 2015 pid=321"..., 92) = 92
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2335, ...}) = 0
write(1, "Sun May 24 20:51:41 2015 pid=321"..., 52) = 52
--
rt_sigaction(SIGKILL, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGUSR1, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGSEGV, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGUSR2, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGPIPE, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGALRM, NULL, {0x7f45f2d08de0, [], SA_RESTORER, 0x7f45f1efa670}, 8) = 0
rt_sigaction(SIGALRM, {SIG_DFL, [], SA_RESTORER, 0x7f45f1efa670}, {0x7f45f2d08de0, [], SA_RESTORER, 0x7f45f1efa670}, 8) = 0
rt_sigaction(SIGTERM, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGSTKFLT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGCONT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGSTOP, NULL, {SIG_DFL, [], 0}, 8) = 0

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