[ will apply this patch to cr_tests unless Matt has comments ]
Freezing the robust futex waiters makes the syscall return with
-EINTR. The task then ends up caling futex_wait_restart. If
the futex value has already been changed by the parent, then
the futex_wait_restart will return -EAGAIN.
If that happens, have the kid create a file called 'TBROK'
and exit so the parent can reap it. The run.sh shell is
rewritten so it will rerun the test if the file TBROK has
been created.
(note this has little to do with c/r, but rather with how
the freezer affects the futex api)
To recreate a hang with the robust testcase without this fix,
run the following script:
==============================================================
#!/bin/bash
#set -e
TEST=robust
source ../common.sh
lcv=0
while [ $lcv -lt 100 ]; do
echo loop num $lcv
rm -f ./checkpoint-*
rm -f TBROK
./${TEST} &
TEST_PID=$!
while [ '!' -r "./checkpoint-ready" ]; do
sleep 1
done
freeze
echo ckpt $TEST_PID
ckpt $TEST_PID > checkpoint-${TEST}
thaw
touch "./checkpoint-done"
wait ${TEST_PID}
retval=$?
if [ -f "TBROK" ]; then
echo "XXX Futex snafu, re-running this test XXX"
lcv=$((lcv-1))
continue
fi
echo "Test ${TEST} done, returned $retval"
if [ $retval -ne 0 ]; then
echo FAIL
exit 1
else
echo PASS
fi
lcv=$((lcv+1))
done
Signed-off-by: Serge Hallyn <[email protected]>
---
futex/robust.c | 10 +++++++++-
futex/run.sh | 13 +++++++++++--
2 files changed, 20 insertions(+), 3 deletions(-)
diff --git a/futex/robust.c b/futex/robust.c
index a52f638..6a5da78 100644
--- a/futex/robust.c
+++ b/futex/robust.c
@@ -103,10 +103,11 @@ void add_rfutex(struct futex *rf)
void acquire_rfutex(struct futex *rf, pid_t tid)
{
- int val = 0;
+ int oldval, newval, val = 0;
rlist.list_op_pending = &rf->rlist; /* ARCH TODO make sure this
assignment is atomic */
+ oldval = atomic_read(&rf->tid);
tid = tid & FUTEX_TID_MASK;
do {
val = atomic_cmpxchg(&rf->tid, 0, tid);
@@ -134,6 +135,13 @@ void acquire_rfutex(struct futex *rf, pid_t tid)
continue;
case EAGAIN:
log("WARN", "EAGAIN while sleeping on futex\n");
+ newval = atomic_read(&rf->tid);
+ if (newval != oldval) {
+ int ret = creat("TBROK", 0755);
+ if (ret == -1)
+ fail++;
+ return;
+ }
continue;
case EINTR:
log("WARN", "EINTR while sleeping on futex\n");
diff --git a/futex/run.sh b/futex/run.sh
index 1ed23ad..1545841 100755
--- a/futex/run.sh
+++ b/futex/run.sh
@@ -37,9 +37,13 @@ fi
# mkdir /cg/1
# chown -R $(id --name -u).$(id --name -g) /cg/1
-for T in ${tes...@]} ; do
+numtests=${#tes...@]}
+CURTEST=0
+
+while [ $CURTEST -lt $NUMTESTS ]; do
+ T=${TESTS[$CURTEST]}
trap 'break' ERR EXIT
- rm -f ./checkpoint-*
+ rm -f ./checkpoint-* TBROK
echo "Running test: ${T}"
./${T} &
TEST_PID=$!
@@ -53,6 +57,10 @@ for T in ${tes...@]} ; do
wait ${TEST_PID}
retval=$?
echo "Test ${T} done, returned $retval"
+ if [ -f "TBROK" ]; then
+ echo "BROK: Futex snafu, re-running this test"
+ continue
+ fi
if [ $retval -ne 0 ]; then
echo FAIL
exit 1
@@ -71,6 +79,7 @@ for T in ${tes...@]} ; do
echo PASS
fi
trap "" ERR EXIT
+ CURTEST=$((CURTEST+1))
done
#rm -f ./checkpoint-*
--
1.6.1.1
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