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Find processes executing futex with FUTEX_WAIT (helps find deadlock-ed processes)
# Find all processes that are executing a futex(2) call with op=FUTEX_WAIT
# In some cases this can be helpful in finding deadlock-ed processes.
test ! $UID -eq 0 && echo -e "WARNING: Not running as root, only processes for this user are being scanned\n" >&2;
pids=$(ps -u $UID -opid --no-headers)
for pid in $pids; do
# subshell already exited before script done
# so cat /proc/<subsell pid> will get error
# cat: /proc/xxxxx/syscall: No such file or directory
if [ "$sub_pid" != "$pid" ]; then
cat /proc/$pid/syscall |
awk "{if (\$1 == 202 && \$3 == \"0x0\") {
print $pid
# $1 is the syscall, we compare to 202 which is the futex call
# See: /usr/include/asm/unistd.h
# $2 is the 1st param, $3 is the 2nd param, etc
# We compare the second param to 0x0 which is FUTEX_WAIT
# See: /usr/include/linux/futex.h
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