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samba-mirror/ctdb/config/debug_locks.sh
Martin Schwenke 6456b06294 ctdb-scripts: Lock debugging should print kernel stack for process in D state
Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Michael Adam <obnox@samba.org>
2015-10-16 13:35:10 +02:00

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#!/bin/sh
# This script parses /proc/locks and finds the processes that are holding
# locks on CTDB databases. For all those processes the script dumps a
# stack trace.
#
# This script can be used only if Samba is configured to use fcntl locks
# rather than mutex locks.
[ -n "$CTDB_BASE" ] || \
export CTDB_BASE=$(cd -P $(dirname "$0") ; echo "$PWD")
. "$CTDB_BASE/functions"
# Default fallback location for database directories.
# These can be overwritten from CTDB configuration
CTDB_DBDIR="${CTDB_VARDIR}"
CTDB_DBDIR_PERSISTENT="${CTDB_VARDIR}/persistent"
loadconfig ctdb
(
flock -n 9 || exit 1
echo "===== Start of debug locks PID=$$ ====="
# Create sed expression to convert inodes to names
sed_cmd=$( ls -li "$CTDB_DBDIR"/*.tdb.* "$CTDB_DBDIR_PERSISTENT"/*.tdb.* |
sed -e "s#${CTDB_DBDIR}/\(.*\)#\1#" \
-e "s#${CTDB_DBDIR_PERSISTENT}/\(.*\)#\1#" |
awk '{printf "s#[0-9a-f]*:[0-9a-f]*:%s #%s #\n", $1, $10}' )
# Parse /proc/locks and extract following information
# pid process_name tdb_name offsets [W]
out=$( cat /proc/locks |
grep -F "POSIX ADVISORY WRITE" |
awk '{ if($2 == "->") { print $6, $7, $8, $9, "W" } else { print $5, $6, $7, $8 } }' |
while read pid rest ; do
pname=$(readlink /proc/$pid/exe)
echo $pid $pname $rest
done | sed -e "$sed_cmd" | grep "\.tdb" )
if [ -n "$out" ]; then
# Log information about locks
echo "$out"
# Find processes that are waiting for locks
dbs=$(echo "$out" | grep "W$" | awk '{print $3}')
all_pids=""
for db in $dbs ; do
pids=$(echo "$out" | grep -v "W$" | grep "$db" | grep -v ctdbd | awk '{print $1}')
all_pids="$all_pids $pids"
done
pids=$(echo $all_pids | tr " " "\n" | sort -u)
# For each process waiting, log stack trace
for pid in $pids ; do
echo "----- Stack trace for PID=$pid -----"
read x x state x </proc/$pid/stat
if [ "$state" = "D" ] ; then
# Don't run gstack on a process in D state since
# gstack will hang until the process exits D state.
# Although it is possible for a process to transition
# to D state after this check, it is unlikely because
# if a process is stuck in D state then it is probably
# the reason why this script was called. Note that a
# kernel stack almost certainly won't help diagnose a
# deadlock... but it will probably give us someone to
# blame!
echo "----- Process in D state, printing kernel stack only"
cat /proc/$pid/stack
else
gstack $pid
# gcore -o /var/log/core-deadlock-ctdb $pid
fi
done
fi
echo "===== End of debug locks PID=$$ ====="
)9>"${CTDB_SCRIPT_VARDIR}/debug_locks.lock" | script_log "ctdbd-lock"
exit 0