[PATCH] memtx: cancel checkpoint thread at exit
Vladimir Davydov
vdavydov.dev at gmail.com
Thu Apr 18 18:46:54 MSK 2019
If a tarantool instance exits while checkpointing is in progress, the
memtx checkpoint thread, which writes the snap file, can access already
freed data resulting in a crash. Let's fix this the same way we did for
relay and vinyl threads - simply cancel the thread forcefully and wait
for it to terminate.
Closes #4170
---
https://github.com/tarantool/tarantool/issues/4170
https://github.com/tarantool/tarantool/commits/dv/gh-4170-memtx-cancel-checkpoint-thread-at-exit
src/box/memtx_engine.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/src/box/memtx_engine.c b/src/box/memtx_engine.c
index 48f700a0..2b9bef24 100644
--- a/src/box/memtx_engine.c
+++ b/src/box/memtx_engine.c
@@ -52,6 +52,9 @@
/* sync snapshot every 16MB */
#define SNAP_SYNC_INTERVAL (1 << 24)
+static void
+checkpoint_cancel(struct checkpoint *ckpt);
+
/*
* Memtx yield-in-transaction trigger: roll back the effects
* of the transaction and mark the transaction as aborted.
@@ -179,6 +182,8 @@ static void
memtx_engine_shutdown(struct engine *engine)
{
struct memtx_engine *memtx = (struct memtx_engine *)engine;
+ if (memtx->checkpoint != NULL)
+ checkpoint_cancel(memtx->checkpoint);
mempool_destroy(&memtx->iterator_pool);
if (mempool_is_initialized(&memtx->rtree_iterator_pool))
mempool_destroy(&memtx->rtree_iterator_pool);
@@ -590,6 +595,11 @@ checkpoint_new(const char *snap_dirname, uint64_t snap_io_rate_limit)
xdir_create(&ckpt->dir, snap_dirname, SNAP, &INSTANCE_UUID, &opts);
vclock_create(&ckpt->vclock);
ckpt->touch = false;
+ /*
+ * Reset the checkpoint thread id so that checkpoint_cancel()
+ * doesn't attempt to cancel the thread if it isn't running.
+ */
+ ckpt->cord.id = 0;
return ckpt;
}
@@ -605,6 +615,19 @@ checkpoint_delete(struct checkpoint *ckpt)
free(ckpt);
}
+static void
+checkpoint_cancel(struct checkpoint *ckpt)
+{
+ /*
+ * Cancel the checkpoint thread if it's running and wait
+ * for it to terminate so as to eliminate the possibility
+ * of use-after-free.
+ */
+ if (ckpt->cord.id != 0 &&
+ tt_pthread_cancel(ckpt->cord.id) != ESRCH)
+ tt_pthread_join(ckpt->cord.id, NULL);
+ checkpoint_delete(ckpt);
+}
static int
checkpoint_add_space(struct space *sp, void *data)
--
2.11.0
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