[dm-devel] [PATCH] multipathd: fix compilation issue with liburcu < 0.8
Benjamin Marzinski
bmarzins at redhat.com
Thu May 13 16:35:59 UTC 2021
On Wed, May 12, 2021 at 11:17:05PM +0200, mwilck at suse.com wrote:
> From: Martin Wilck <mwilck at suse.com>
>
> 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 at suse.com>
> ---
> multipathd/Makefile | 2 ++
> multipathd/main.c | 17 +++++++++++++++--
> 2 files changed, 17 insertions(+), 2 deletions(-)
>
> diff --git a/multipathd/Makefile b/multipathd/Makefile
> index d053c1e..dc7eb32 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 pkg-config --modversion liburcu 2>/dev/null | \
> + awk -F. '{ printf("-DURCU_VERSION=0x%06x\n", 256 * ( 256 * $$1 + $$2) + $$3); }')
Shouldn't this be
$(shell $(PKGCONFIG) --modversion ...
-Ben
>
> ifdef SYSTEMD
> CFLAGS += -DUSE_SYSTEMD=$(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
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