This patch is to prevent deadlocks when multiple bpf programs are attached to queued_spin_locks functions. This issue is similar to what is already discussed [1] before with the spin_lock helpers. The addition of notrace macro to the queued_spin_locks has been discussed [2] when bpf_spin_locks are introduced. [1] https://lore.kernel.org/bpf/CAE5sdEigPnoGrzN8WU7Tx-h-iFuMZgW06qp0KHWtpvoXxf1OAQ@xxxxxxxxxxxxxx/#r [2] https://lore.kernel.org/all/20190117011629.efxp7abj4bpf5yco@ast-mbp/t/#maf05c4d71f935f3123013b7ed410e4f50e9da82c Fixes: d83525ca62cf ("bpf: introduce bpf_spin_lock") Signed-off-by: Siddharth Chintamaneni <sidchintamaneni@xxxxxx> --- kernel/locking/qspinlock.c | 2 +- .../bpf/prog_tests/tracing_failure.c | 24 +++++++++++++++++++ .../selftests/bpf/progs/tracing_failure.c | 6 +++++ 3 files changed, 31 insertions(+), 1 deletion(-) diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index ebe6b8ec7cb3..4d46538d8399 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -313,7 +313,7 @@ static __always_inline u32 __pv_wait_head_or_lock(struct qspinlock *lock, * contended : (*,x,y) +--> (*,0,0) ---> (*,0,1) -' : * queue : ^--' : */ -void __lockfunc queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) +notrace void __lockfunc queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) { struct mcs_spinlock *prev, *next, *node; u32 old, tail; diff --git a/tools/testing/selftests/bpf/prog_tests/tracing_failure.c b/tools/testing/selftests/bpf/prog_tests/tracing_failure.c index a222df765bc3..822ee6c559bc 100644 --- a/tools/testing/selftests/bpf/prog_tests/tracing_failure.c +++ b/tools/testing/selftests/bpf/prog_tests/tracing_failure.c @@ -28,10 +28,34 @@ static void test_bpf_spin_lock(bool is_spin_lock) tracing_failure__destroy(skel); } +static void test_queued_spin_lock(void) +{ + struct tracing_failure *skel; + int err; + + skel = tracing_failure__open(); + if (!ASSERT_OK_PTR(skel, "tracing_failure__open")) + return; + + bpf_program__set_autoload(skel->progs.test_queued_spin_lock, true); + + err = tracing_failure__load(skel); + if (!ASSERT_OK(err, "tracing_failure__load")) + goto out; + + err = tracing_failure__attach(skel); + ASSERT_ERR(err, "tracing_failure__attach"); + +out: + tracing_failure__destroy(skel); +} + void test_tracing_failure(void) { if (test__start_subtest("bpf_spin_lock")) test_bpf_spin_lock(true); if (test__start_subtest("bpf_spin_unlock")) test_bpf_spin_lock(false); + if (test__start_subtest("queued_spin_lock_slowpath")) + test_queued_spin_lock(); } diff --git a/tools/testing/selftests/bpf/progs/tracing_failure.c b/tools/testing/selftests/bpf/progs/tracing_failure.c index d41665d2ec8c..2d2e7fc9d4f0 100644 --- a/tools/testing/selftests/bpf/progs/tracing_failure.c +++ b/tools/testing/selftests/bpf/progs/tracing_failure.c @@ -18,3 +18,9 @@ int BPF_PROG(test_spin_unlock, struct bpf_spin_lock *lock) { return 0; } + +SEC("?fentry/queued_spin_lock_slowpath") +int BPF_PROG(test_queued_spin_lock, struct qspinlock *lock, u32 val) +{ + return 0; +} -- 2.43.0
