problem in show engine innodb status (no replies)

i read the innodb code about how to get the rw s/x lock and mutex

and here is a question about "show engine innodb status" output of SEMAPHORES session,i do not know the mutex rounds is what?,

mutex_spin_wait_count is how many times thread do spin wait,and mutex_os_wait_count is how many times thread ask for wait array cell,and sleep
but i do not know what the mutex rounds means ??
anyone can explain ?

from code

fprintf(file,
"Mutex spin waits %lu, rounds %lu, OS waits %lu\n"
"RW-shared spins %lu, OS waits %lu;"
" RW-excl spins %lu, OS waits %lu\n",
(ulong) mutex_spin_wait_count,
(ulong) mutex_spin_round_count,
(ulong) mutex_os_wait_count,
(ulong) rw_s_spin_wait_count,
(ulong) rw_s_os_wait_count,
(ulong) rw_x_spin_wait_count,
(ulong) rw_x_os_wait_count);

----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 4415, signal count 4413
Mutex spin waits 0, rounds 9917, OS waits 122
RW-shared spins 8540, OS waits 4248; RW-excl spins 44, OS waits 39