write(1, "setting main handler\n", 21setting main handler
)  = 21
rt_sigprocmask(SIG_BLOCK, [ALRM], [], 8) = 0
rt_sigaction(SIGALRM, {0x713790, [], 0}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
write(1, "set main handler\n", 17set main handler
)      = 17
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7f42b08) = 8291
write(1, "sub f start\n", 12sub f start
)           = 12
rt_sigprocmask(SIG_BLOCK, [ALRM], [], 8) = 0
rt_sigaction(SIGALRM, {SIG_DFL}, {0x713790, [], 0}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [ALRM], [], 8) = 0
rt_sigaction(SIGALRM, {0x713790, [], 0}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
write(1, "sub f end\n", 10sub f end
)             = 10
rt_sigprocmask(SIG_BLOCK, [ALRM], [], 8) = 0
rt_sigaction(SIGALRM, {0x713790, [], 0}, {0x713790, [], 0}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
write(1, "sub f start\n", 12sub f start
)           = 12
rt_sigprocmask(SIG_BLOCK, [ALRM], [], 8) = 0
rt_sigaction(SIGALRM, {SIG_DFL}, {0x713790, [], 0}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [ALRM], [], 8) = 0 
rt_sigaction(SIGALRM, {0x713790, [], 0}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
write(1, "sub f end\n", 10sub f end
)             = 10
rt_sigprocmask(SIG_BLOCK, [ALRM], [], 8) = 0
rt_sigaction(SIGALRM, {0x713790, [], 0}, {0x713790, [], 0}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
write(1, "sub f start\n", 12sub f start
)           = 12
rt_sigprocmask(SIG_BLOCK, [ALRM], [], 8) = 0
rt_sigaction(SIGALRM, {SIG_DFL}, {0x713790, [], 0}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [ALRM], [], 8) = 0
rt_sigaction(SIGALRM, {0x713790, [], 0}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
write(1, "sub f end\n", 10sub f end
)             = 10
rt_sigprocmask(SIG_BLOCK, [ALRM], [], 8) = 0
rt_sigaction(SIGALRM, {0x713790, [], 0}, {0x713790, [], 0}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
write(1, "sub f start\n", 12sub f start
)           = 12
rt_sigprocmask(SIG_BLOCK, [ALRM], [], 8) = 0
rt_sigaction(SIGALRM, {SIG_DFL}, {0x713790, [], 0}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [ALRM], [], 8) = 0
rt_sigaction(SIGALRM, {0x713790, [], 0}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
write(1, "sub f end\n", 10sub f end