From: Martin Wilck <mwilck@xxxxxxxx> To avoid race conditions with pending RCU callbacks on exit, it's necessary to call rcu_barrier() in cleanup_rcu() (see https://lists.lttng.org/pipermail/lttng-dev/2021-May/029958.html and follow-ups). rcu_barrier() is only available in User-space RCU v0.8 and newer. Fix it by reverting 5d0dae6 ("multipathd: Fix liburcu memory leak") if an older version of liburcu is detected. Fixes: 5d0dae6 ("multipathd: Fix liburcu memory leak") Signed-off-by: Martin Wilck <mwilck@xxxxxxxx> --- v2: Use $(PKGCONFIG) (Ben Marzinski); remove "\n" in awk. --- multipathd/Makefile | 2 ++ multipathd/main.c | 17 +++++++++++++++-- 2 files changed, 17 insertions(+), 2 deletions(-) diff --git a/multipathd/Makefile b/multipathd/Makefile index d053c1e..393b6cb 100644 --- a/multipathd/Makefile +++ b/multipathd/Makefile @@ -16,6 +16,8 @@ LDFLAGS += $(BIN_LDFLAGS) LIBDEPS += -L$(multipathdir) -lmultipath -L$(mpathpersistdir) -lmpathpersist \ -L$(mpathcmddir) -lmpathcmd -ludev -ldl -lurcu -lpthread \ -ldevmapper -lreadline +CFLAGS += $(shell $(PKGCONFIG) --modversion liburcu 2>/dev/null | \ + awk -F. '{ printf("-DURCU_VERSION=0x%06x", 256 * ( 256 * $$1 + $$2) + $$3); }') ifdef SYSTEMD CFLAGS += -DUSE_SYSTEMD=$(SYSTEMD) diff --git a/multipathd/main.c b/multipathd/main.c index 102946b..c34fd9c 100644 --- a/multipathd/main.c +++ b/multipathd/main.c @@ -3031,6 +3031,10 @@ static void cleanup_threads(void) pthread_attr_destroy(&waiter_attr); } +#ifndef URCU_VERSION +# define URCU_VERSION 0 +#endif +#if (URCU_VERSION >= 0x000800) /* * Use a non-default call_rcu_data for child(). * @@ -3040,6 +3044,9 @@ static void cleanup_threads(void) * can't be joined with pthread_join(), leaving a memory leak. * * Therefore we create our own, which can be destroyed and joined. + * The cleanup handler needs to call rcu_barrier(), which is only + * available in user-space RCU v0.8 and newer. See + * https://lists.lttng.org/pipermail/lttng-dev/2021-May/029958.html */ static struct call_rcu_data *setup_rcu(void) { @@ -3072,6 +3079,7 @@ static void cleanup_rcu(void) } rcu_unregister_thread(); } +#endif /* URCU_VERSION */ static void cleanup_child(void) { @@ -3116,9 +3124,14 @@ child (__attribute__((unused)) void *param) init_unwinder(); mlockall(MCL_CURRENT | MCL_FUTURE); signal_init(); +#if (URCU_VERSION >= 0x000800) mp_rcu_data = setup_rcu(); - - if (atexit(cleanup_rcu) || atexit(cleanup_child)) + if (atexit(cleanup_rcu)) + fprintf(stderr, "failed to register RCU cleanup handler\n"); +#else + rcu_init(); +#endif + if (atexit(cleanup_child)) fprintf(stderr, "failed to register cleanup handlers\n"); setup_thread_attr(&misc_attr, 64 * 1024, 0); -- 2.31.1 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel
