On Mon, Dec 22, 2025 at 4:30 AM Waiman Long <[email protected]> wrote: > > > On 12/21/25 7:26 AM, Li Wang wrote: > > The hugetlb cgroup usage wait loops in charge_reserved_hugetlb.sh were > > unbounded and could hang forever if the expected cgroup file value never > > appears (e.g. due to write_to_hugetlbfs in Error mapping). > > > > --- Error log --- > > # uname -r > > 6.12.0-xxx.el10.aarch64+64k > > > > # ls /sys/kernel/mm/hugepages/hugepages-* > > hugepages-16777216kB/ hugepages-2048kB/ hugepages-524288kB/ > > > > #./charge_reserved_hugetlb.sh -cgroup-v2 > > # ----------------------------------------- > > ... > > # nr hugepages = 10 > > # writing cgroup limit: 5368709120 > > # writing reseravation limit: 5368709120 > > ... > > # write_to_hugetlbfs: Error mapping the file: Cannot allocate memory > > # Waiting for hugetlb memory reservation to reach size 2684354560. > > # 0 > > # Waiting for hugetlb memory reservation to reach size 2684354560. > > # 0 > > # Waiting for hugetlb memory reservation to reach size 2684354560. > > # 0 > > # Waiting for hugetlb memory reservation to reach size 2684354560. > > # 0 > > # Waiting for hugetlb memory reservation to reach size 2684354560. > > # 0 > > # Waiting for hugetlb memory reservation to reach size 2684354560. > > # 0 > > ... > > > > Introduce a small helper, wait_for_file_value(), and use it for: > > - waiting for reservation usage to drop to 0, > > - waiting for reservation usage to reach a given size, > > - waiting for fault usage to reach a given size. > > > > This makes the waits consistent and adds a hard timeout (60 tries with > > 1s sleep) so the test fails instead of stalling indefinitely. > > > > Signed-off-by: Li Wang <[email protected]> > > Cc: David Hildenbrand <[email protected]> > > Cc: Mark Brown <[email protected]> > > Cc: Shuah Khan <[email protected]> > > Cc: Waiman Long <[email protected]> > > --- > > .../selftests/mm/charge_reserved_hugetlb.sh | 51 +++++++++++-------- > > 1 file changed, 30 insertions(+), 21 deletions(-) > > > > diff --git a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh > > b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh > > index fa6713892d82..447769657634 100755 > > --- a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh > > +++ b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh > > @@ -100,7 +100,7 @@ function setup_cgroup() { > > echo writing cgroup limit: "$cgroup_limit" > > echo "$cgroup_limit" > > >$cgroup_path/$name/hugetlb.${MB}MB.$fault_limit_file > > > > - echo writing reseravation limit: "$reservation_limit" > > + echo writing reservation limit: "$reservation_limit" > > echo "$reservation_limit" > \ > > $cgroup_path/$name/hugetlb.${MB}MB.$reservation_limit_file > > > > @@ -112,41 +112,50 @@ function setup_cgroup() { > > fi > > } > > > > +function wait_for_file_value() { > > + local path="$1" > > + local expect="$2" > > + local max_tries=60 > > + > > + if [[ ! -r "$path" ]]; then > > + echo "ERROR: cannot read '$path', missing or permission denied" > > + return 1 > > + fi > > + > > + for ((i=1; i<=max_tries; i++)); do > > + local cur="$(cat "$path")" > > + if [[ "$cur" == "$expect" ]]; then > > + return 0 > > + fi > > + echo "Waiting for $path to become '$expect' (current: '$cur') (try > > $i/$max_tries)" > > + sleep 1 > > + done > > + > > + echo "ERROR: timeout waiting for $path to become '$expect'" > > + return 1 > > +} > > + > > function wait_for_hugetlb_memory_to_get_depleted() { > > local cgroup="$1" > > local > > path="$cgroup_path/$cgroup/hugetlb.${MB}MB.$reservation_usage_file" > > - # Wait for hugetlbfs memory to get depleted. > > - while [ $(cat $path) != 0 ]; do > > - echo Waiting for hugetlb memory to get depleted. > > - cat $path > > - sleep 0.5 > > - done > > + > > + wait_for_file_value "$path" "0" > > } > > > > function wait_for_hugetlb_memory_to_get_reserved() { > > local cgroup="$1" > > local size="$2" > > - > > local > > path="$cgroup_path/$cgroup/hugetlb.${MB}MB.$reservation_usage_file" > > - # Wait for hugetlbfs memory to get written. > > - while [ $(cat $path) != $size ]; do > > - echo Waiting for hugetlb memory reservation to reach size $size. > > - cat $path > > - sleep 0.5 > > - done > > + > > + wait_for_file_value "$path" "$size" > > } > > > > function wait_for_hugetlb_memory_to_get_written() { > > local cgroup="$1" > > local size="$2" > > - > > local path="$cgroup_path/$cgroup/hugetlb.${MB}MB.$fault_usage_file" > > - # Wait for hugetlbfs memory to get written. > > - while [ $(cat $path) != $size ]; do > > - echo Waiting for hugetlb memory to reach size $size. > > - cat $path > > - sleep 0.5 > > - done > > + > > + wait_for_file_value "$path" "$size" > > } > > > > function write_hugetlbfs_and_get_usage() { > > wait_for_file_value() now return 0 onr success and 1 on timeout. > However, none of the callers of the wait_for_hugetlb_memory* are > checking their return values and acting accordingly. Are we expecting > that the test will show failure because the waiting isn't completed or > should we explicitly exit with ksft_fail (1) value?
Hmm, it seems the test shouldn't exit too early. As the wait_for_hugetlb_memory* is only trying 60s to examine the file value, if timeouted, we still need to keep going because the test requires CLEANUP work and exit/report from there. The key point of each subtest is to save the '$write_result' value and examine it which controls the whole test to exit. e.g. This is an intentional error test: # ./charge_reserved_hugetlb.sh -cgroup-v2 CLEANUP DONE ... Writing to this path: /mnt/huge/test Writing this size: 2684354560 Not populating. Not writing to memory. Using method=0 Shared mapping. RESERVE mapping. Allocating using HUGETLBFS. write_to_hugetlbfs: Error mapping the file: Cannot allocate memory Waiting for /sys/fs/cgroup/hugetlb_cgroup_test/hugetlb.512MB.rsvd.current to become '2684354560' (current: '0') (try 1/60) Waiting for /sys/fs/cgroup/hugetlb_cgroup_test/hugetlb.512MB.rsvd.current to become '2684354560' (current: '0') (try 2/60) Waiting for /sys/fs/cgroup/hugetlb_cgroup_test/hugetlb.512MB.rsvd.current to become '2684354560' (current: '0') (try 3/60) Waiting for /sys/fs/cgroup/hugetlb_cgroup_test/hugetlb.512MB.rsvd.current to become '2684354560' (current: '0') (try 4/60) ... Waiting for /sys/fs/cgroup/hugetlb_cgroup_test/hugetlb.512MB.rsvd.current to become '2684354560' (current: '0') (try 60/60) ERROR: timeout waiting for /sys/fs/cgroup/hugetlb_cgroup_test/hugetlb.512MB.rsvd.current to become '2684354560' After write: hugetlb_usage=0 reserved_usage=0 0 0 Memory charged to hugtlb=0 Memory charged to reservation=0 expected (2684354560) != actual (0): Reserved memory not charged to reservation usage. CLEANUP DONE -- Regards, Li Wang
