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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Benjamin Marzinski <bmarzins@redhat.com>
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Date: Fri, 23 Oct 2020 11:38:24 -0500
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Subject: [PATCH] libmultipath: don't dlclose tur checker DSO
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The multipathd tur checker thread is designed to be able to finish at
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any time, even after the tur checker itself has been freed. The
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multipathd shutdown code makes sure all the checkers have been freed
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before freeing the checker_class and calling dlclose() to unload the
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DSO, but this doesn't guarantee that the checker threads have finished.
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If one hasn't, the DSO will get unloaded while the thread still running
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code from it, causing a segfault. Unfortunately, it's not possible to be
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sure that all tur checker threads have ended during shutdown, without
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making them joinable.
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However, since libmultipath will never be reinitialized after it has
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been uninitialzed, not dlclosing the tur checker DSO once a thread is
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started has minimal cost (keeping the DSO code around until the program
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exits, which usually happens right after freeing the checkers).
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Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
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---
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libmultipath/checkers.c | 10 +++++++++-
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libmultipath/checkers.h | 1 +
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libmultipath/checkers/tur.c | 1 +
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3 files changed, 11 insertions(+), 1 deletion(-)
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diff --git a/libmultipath/checkers.c b/libmultipath/checkers.c
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index 8d2be8a9..6359e5d8 100644
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--- a/libmultipath/checkers.c
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+++ b/libmultipath/checkers.c
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@@ -21,6 +21,7 @@ struct checker_class {
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void (*reset)(void); /* to reset the global variables */
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const char **msgtable;
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short msgtable_size;
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+ int keep_dso;
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};
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char *checker_state_names[] = {
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@@ -69,7 +70,7 @@ void free_checker_class(struct checker_class *c)
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list_del(&c->node);
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if (c->reset)
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c->reset();
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- if (c->handle) {
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+ if (c->handle && !c->keep_dso) {
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if (dlclose(c->handle) != 0) {
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condlog(0, "Cannot unload checker %s: %s",
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c->name, dlerror());
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@@ -192,6 +193,13 @@ out:
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return NULL;
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}
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+void checker_keep_dso(struct checker * c)
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+{
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+ if (!c || !c->cls)
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+ return;
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+ c->cls->keep_dso = 1;
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+}
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+
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void checker_set_fd (struct checker * c, int fd)
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{
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if (!c)
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diff --git a/libmultipath/checkers.h b/libmultipath/checkers.h
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index b458118d..f183cff9 100644
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--- a/libmultipath/checkers.h
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+++ b/libmultipath/checkers.h
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@@ -145,6 +145,7 @@ void checker_reset (struct checker *);
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void checker_set_sync (struct checker *);
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void checker_set_async (struct checker *);
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void checker_set_fd (struct checker *, int);
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+void checker_keep_dso(struct checker *c);
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void checker_enable (struct checker *);
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void checker_disable (struct checker *);
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int checker_check (struct checker *, int);
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diff --git a/libmultipath/checkers/tur.c b/libmultipath/checkers/tur.c
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index e886fcf8..fd58d62a 100644
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--- a/libmultipath/checkers/tur.c
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+++ b/libmultipath/checkers/tur.c
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@@ -394,6 +394,7 @@ int libcheck_check(struct checker * c)
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uatomic_set(&ct->running, 1);
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tur_set_async_timeout(c);
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setup_thread_attr(&attr, 32 * 1024, 1);
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+ checker_keep_dso(c);
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r = pthread_create(&ct->thread, &attr, tur_thread, ct);
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pthread_attr_destroy(&attr);
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if (r) {
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--
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2.17.2
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