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
--- SIGALRM (Alarm clock) @ 0 (0) ---
sigreturn()                             = ? (mask now [])
rt_sigprocmask(SIG_BLOCK, [ALRM], NULL, 8) = 0
write(1, "SIGALRM: sub handler\n", 21SIGALRM: sub handler
)  = 21
rt_sigprocmask(SIG_UNBLOCK, [ALRM], 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