* Lidong Chen (jemmy858...@gmail.com) wrote:
> From: Lidong Chen <jemmy858...@gmail.com>
>
> This patch implements bi-directional RDMA QIOChannel. Because different
> threads may access RDMAQIOChannel currently, this patch use RCU to protect it.
>
> Signed-off-by: Lidong Chen <lidongc...@tencent.com>
Paolo: Does it make sense the way RCU is used here Holding the
read-lock for so long in multifd_rdma_[read|write]v is what worries me
most.
Dave
> ---
> migration/colo.c | 2 +
> migration/migration.c | 2 +
> migration/postcopy-ram.c | 2 +
> migration/ram.c | 4 +
> migration/rdma.c | 196
> ++++++++++++++++++++++++++++++++++++++++-------
> migration/savevm.c | 3 +
> 6 files changed, 183 insertions(+), 26 deletions(-)
>
> diff --git a/migration/colo.c b/migration/colo.c
> index 4381067..88936f5 100644
> --- a/migration/colo.c
> +++ b/migration/colo.c
> @@ -534,6 +534,7 @@ void *colo_process_incoming_thread(void *opaque)
> uint64_t value;
> Error *local_err = NULL;
>
> + rcu_register_thread();
> qemu_sem_init(&mis->colo_incoming_sem, 0);
>
> migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
> @@ -666,5 +667,6 @@ out:
> }
> migration_incoming_exit_colo();
>
> + rcu_unregister_thread();
> return NULL;
> }
> diff --git a/migration/migration.c b/migration/migration.c
> index 1d0aaec..4253d9f 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -2028,6 +2028,7 @@ static void *source_return_path_thread(void *opaque)
> int res;
>
> trace_source_return_path_thread_entry();
> + rcu_register_thread();
>
> retry:
> while (!ms->rp_state.error && !qemu_file_get_error(rp) &&
> @@ -2167,6 +2168,7 @@ out:
> trace_source_return_path_thread_end();
> ms->rp_state.from_dst_file = NULL;
> qemu_fclose(rp);
> + rcu_unregister_thread();
> return NULL;
> }
>
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index 48e5155..98613eb 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -853,6 +853,7 @@ static void *postcopy_ram_fault_thread(void *opaque)
> RAMBlock *rb = NULL;
>
> trace_postcopy_ram_fault_thread_entry();
> + rcu_register_thread();
> mis->last_rb = NULL; /* last RAMBlock we sent part of */
> qemu_sem_post(&mis->fault_thread_sem);
>
> @@ -1059,6 +1060,7 @@ retry:
> }
> }
> }
> + rcu_unregister_thread();
> trace_postcopy_ram_fault_thread_exit();
> g_free(pfd);
> return NULL;
> diff --git a/migration/ram.c b/migration/ram.c
> index a500015..a674fb5 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -683,6 +683,7 @@ static void *multifd_send_thread(void *opaque)
> MultiFDSendParams *p = opaque;
> Error *local_err = NULL;
>
> + rcu_register_thread();
> if (multifd_send_initial_packet(p, &local_err) < 0) {
> goto out;
> }
> @@ -706,6 +707,7 @@ out:
> p->running = false;
> qemu_mutex_unlock(&p->mutex);
>
> + rcu_unregister_thread();
> return NULL;
> }
>
> @@ -819,6 +821,7 @@ static void *multifd_recv_thread(void *opaque)
> {
> MultiFDRecvParams *p = opaque;
>
> + rcu_register_thread();
> while (true) {
> qemu_mutex_lock(&p->mutex);
> if (p->quit) {
> @@ -833,6 +836,7 @@ static void *multifd_recv_thread(void *opaque)
> p->running = false;
> qemu_mutex_unlock(&p->mutex);
>
> + rcu_unregister_thread();
> return NULL;
> }
>
> diff --git a/migration/rdma.c b/migration/rdma.c
> index f6705a3..769f443 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -86,6 +86,7 @@ static uint32_t known_capabilities =
> RDMA_CAPABILITY_PIN_ALL;
> " to abort!"); \
> rdma->error_reported = 1; \
> } \
> + rcu_read_unlock(); \
> return rdma->error_state; \
> } \
> } while (0)
> @@ -402,7 +403,8 @@ typedef struct QIOChannelRDMA QIOChannelRDMA;
>
> struct QIOChannelRDMA {
> QIOChannel parent;
> - RDMAContext *rdma;
> + RDMAContext *rdmain;
> + RDMAContext *rdmaout;
> QEMUFile *file;
> bool blocking; /* XXX we don't actually honour this yet */
> };
> @@ -2630,12 +2632,20 @@ static ssize_t qio_channel_rdma_writev(QIOChannel
> *ioc,
> {
> QIOChannelRDMA *rioc = QIO_CHANNEL_RDMA(ioc);
> QEMUFile *f = rioc->file;
> - RDMAContext *rdma = rioc->rdma;
> + RDMAContext *rdma;
> int ret;
> ssize_t done = 0;
> size_t i;
> size_t len = 0;
>
> + rcu_read_lock();
> + rdma = atomic_rcu_read(&rioc->rdmaout);
> +
> + if (!rdma) {
> + rcu_read_unlock();
> + return -EIO;
> + }
> +
> CHECK_ERROR_STATE();
>
> /*
> @@ -2645,6 +2655,7 @@ static ssize_t qio_channel_rdma_writev(QIOChannel *ioc,
> ret = qemu_rdma_write_flush(f, rdma);
> if (ret < 0) {
> rdma->error_state = ret;
> + rcu_read_unlock();
> return ret;
> }
>
> @@ -2664,6 +2675,7 @@ static ssize_t qio_channel_rdma_writev(QIOChannel *ioc,
>
> if (ret < 0) {
> rdma->error_state = ret;
> + rcu_read_unlock();
> return ret;
> }
>
> @@ -2672,6 +2684,7 @@ static ssize_t qio_channel_rdma_writev(QIOChannel *ioc,
> }
> }
>
> + rcu_read_unlock();
> return done;
> }
>
> @@ -2705,12 +2718,20 @@ static ssize_t qio_channel_rdma_readv(QIOChannel *ioc,
> Error **errp)
> {
> QIOChannelRDMA *rioc = QIO_CHANNEL_RDMA(ioc);
> - RDMAContext *rdma = rioc->rdma;
> + RDMAContext *rdma;
> RDMAControlHeader head;
> int ret = 0;
> ssize_t i;
> size_t done = 0;
>
> + rcu_read_lock();
> + rdma = atomic_rcu_read(&rioc->rdmain);
> +
> + if (!rdma) {
> + rcu_read_unlock();
> + return -EIO;
> + }
> +
> CHECK_ERROR_STATE();
>
> for (i = 0; i < niov; i++) {
> @@ -2722,7 +2743,7 @@ static ssize_t qio_channel_rdma_readv(QIOChannel *ioc,
> * were given and dish out the bytes until we run
> * out of bytes.
> */
> - ret = qemu_rdma_fill(rioc->rdma, data, want, 0);
> + ret = qemu_rdma_fill(rdma, data, want, 0);
> done += ret;
> want -= ret;
> /* Got what we needed, so go to next iovec */
> @@ -2744,25 +2765,28 @@ static ssize_t qio_channel_rdma_readv(QIOChannel *ioc,
>
> if (ret < 0) {
> rdma->error_state = ret;
> + rcu_read_unlock();
> return ret;
> }
>
> /*
> * SEND was received with new bytes, now try again.
> */
> - ret = qemu_rdma_fill(rioc->rdma, data, want, 0);
> + ret = qemu_rdma_fill(rdma, data, want, 0);
> done += ret;
> want -= ret;
>
> /* Still didn't get enough, so lets just return */
> if (want) {
> if (done == 0) {
> + rcu_read_unlock();
> return QIO_CHANNEL_ERR_BLOCK;
> } else {
> break;
> }
> }
> }
> + rcu_read_unlock();
> return done;
> }
>
> @@ -2814,15 +2838,29 @@ qio_channel_rdma_source_prepare(GSource *source,
> gint *timeout)
> {
> QIOChannelRDMASource *rsource = (QIOChannelRDMASource *)source;
> - RDMAContext *rdma = rsource->rioc->rdma;
> + RDMAContext *rdma;
> GIOCondition cond = 0;
> *timeout = -1;
>
> + rcu_read_lock();
> + if (rsource->condition == G_IO_IN) {
> + rdma = atomic_rcu_read(&rsource->rioc->rdmain);
> + } else {
> + rdma = atomic_rcu_read(&rsource->rioc->rdmaout);
> + }
> +
> + if (!rdma) {
> + error_report("RDMAContext is NULL when prepare Gsource");
> + rcu_read_unlock();
> + return FALSE;
> + }
> +
> if (rdma->wr_data[0].control_len) {
> cond |= G_IO_IN;
> }
> cond |= G_IO_OUT;
>
> + rcu_read_unlock();
> return cond & rsource->condition;
> }
>
> @@ -2830,14 +2868,28 @@ static gboolean
> qio_channel_rdma_source_check(GSource *source)
> {
> QIOChannelRDMASource *rsource = (QIOChannelRDMASource *)source;
> - RDMAContext *rdma = rsource->rioc->rdma;
> + RDMAContext *rdma;
> GIOCondition cond = 0;
>
> + rcu_read_lock();
> + if (rsource->condition == G_IO_IN) {
> + rdma = atomic_rcu_read(&rsource->rioc->rdmain);
> + } else {
> + rdma = atomic_rcu_read(&rsource->rioc->rdmaout);
> + }
> +
> + if (!rdma) {
> + error_report("RDMAContext is NULL when check Gsource");
> + rcu_read_unlock();
> + return FALSE;
> + }
> +
> if (rdma->wr_data[0].control_len) {
> cond |= G_IO_IN;
> }
> cond |= G_IO_OUT;
>
> + rcu_read_unlock();
> return cond & rsource->condition;
> }
>
> @@ -2848,14 +2900,28 @@ qio_channel_rdma_source_dispatch(GSource *source,
> {
> QIOChannelFunc func = (QIOChannelFunc)callback;
> QIOChannelRDMASource *rsource = (QIOChannelRDMASource *)source;
> - RDMAContext *rdma = rsource->rioc->rdma;
> + RDMAContext *rdma;
> GIOCondition cond = 0;
>
> + rcu_read_lock();
> + if (rsource->condition == G_IO_IN) {
> + rdma = atomic_rcu_read(&rsource->rioc->rdmain);
> + } else {
> + rdma = atomic_rcu_read(&rsource->rioc->rdmaout);
> + }
> +
> + if (!rdma) {
> + error_report("RDMAContext is NULL when dispatch Gsource");
> + rcu_read_unlock();
> + return FALSE;
> + }
> +
> if (rdma->wr_data[0].control_len) {
> cond |= G_IO_IN;
> }
> cond |= G_IO_OUT;
>
> + rcu_read_unlock();
> return (*func)(QIO_CHANNEL(rsource->rioc),
> (cond & rsource->condition),
> user_data);
> @@ -2900,15 +2966,32 @@ static int qio_channel_rdma_close(QIOChannel *ioc,
> Error **errp)
> {
> QIOChannelRDMA *rioc = QIO_CHANNEL_RDMA(ioc);
> + RDMAContext *rdmain, *rdmaout;
> trace_qemu_rdma_close();
> - if (rioc->rdma) {
> - if (!rioc->rdma->error_state) {
> - rioc->rdma->error_state = qemu_file_get_error(rioc->file);
> - }
> - qemu_rdma_cleanup(rioc->rdma);
> - g_free(rioc->rdma);
> - rioc->rdma = NULL;
> +
> + rdmain = rioc->rdmain;
> + if (rdmain) {
> + atomic_rcu_set(&rioc->rdmain, NULL);
> + }
> +
> + rdmaout = rioc->rdmaout;
> + if (rdmaout) {
> + atomic_rcu_set(&rioc->rdmaout, NULL);
> }
> +
> + synchronize_rcu();
> +
> + if (rdmain) {
> + qemu_rdma_cleanup(rdmain);
> + }
> +
> + if (rdmaout) {
> + qemu_rdma_cleanup(rdmaout);
> + }
> +
> + g_free(rdmain);
> + g_free(rdmaout);
> +
> return 0;
> }
>
> @@ -2951,12 +3034,21 @@ static size_t qemu_rdma_save_page(QEMUFile *f, void
> *opaque,
> size_t size, uint64_t *bytes_sent)
> {
> QIOChannelRDMA *rioc = QIO_CHANNEL_RDMA(opaque);
> - RDMAContext *rdma = rioc->rdma;
> + RDMAContext *rdma;
> int ret;
>
> + rcu_read_lock();
> + rdma = atomic_rcu_read(&rioc->rdmaout);
> +
> + if (!rdma) {
> + rcu_read_unlock();
> + return -EIO;
> + }
> +
> CHECK_ERROR_STATE();
>
> if (migrate_get_current()->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
> + rcu_read_unlock();
> return RAM_SAVE_CONTROL_NOT_SUPP;
> }
>
> @@ -3041,9 +3133,11 @@ static size_t qemu_rdma_save_page(QEMUFile *f, void
> *opaque,
> }
> }
>
> + rcu_read_unlock();
> return RAM_SAVE_CONTROL_DELAYED;
> err:
> rdma->error_state = ret;
> + rcu_read_unlock();
> return ret;
> }
>
> @@ -3219,8 +3313,8 @@ static int qemu_rdma_registration_handle(QEMUFile *f,
> void *opaque)
> RDMAControlHeader blocks = { .type = RDMA_CONTROL_RAM_BLOCKS_RESULT,
> .repeat = 1 };
> QIOChannelRDMA *rioc = QIO_CHANNEL_RDMA(opaque);
> - RDMAContext *rdma = rioc->rdma;
> - RDMALocalBlocks *local = &rdma->local_ram_blocks;
> + RDMAContext *rdma;
> + RDMALocalBlocks *local;
> RDMAControlHeader head;
> RDMARegister *reg, *registers;
> RDMACompress *comp;
> @@ -3233,8 +3327,17 @@ static int qemu_rdma_registration_handle(QEMUFile *f,
> void *opaque)
> int count = 0;
> int i = 0;
>
> + rcu_read_lock();
> + rdma = atomic_rcu_read(&rioc->rdmain);
> +
> + if (!rdma) {
> + rcu_read_unlock();
> + return -EIO;
> + }
> +
> CHECK_ERROR_STATE();
>
> + local = &rdma->local_ram_blocks;
> do {
> trace_qemu_rdma_registration_handle_wait();
>
> @@ -3468,6 +3571,7 @@ out:
> if (ret < 0) {
> rdma->error_state = ret;
> }
> + rcu_read_unlock();
> return ret;
> }
>
> @@ -3481,10 +3585,18 @@ out:
> static int
> rdma_block_notification_handle(QIOChannelRDMA *rioc, const char *name)
> {
> - RDMAContext *rdma = rioc->rdma;
> + RDMAContext *rdma;
> int curr;
> int found = -1;
>
> + rcu_read_lock();
> + rdma = atomic_rcu_read(&rioc->rdmain);
> +
> + if (!rdma) {
> + rcu_read_unlock();
> + return -EIO;
> + }
> +
> /* Find the matching RAMBlock in our local list */
> for (curr = 0; curr < rdma->local_ram_blocks.nb_blocks; curr++) {
> if (!strcmp(rdma->local_ram_blocks.block[curr].block_name, name)) {
> @@ -3495,6 +3607,7 @@ rdma_block_notification_handle(QIOChannelRDMA *rioc,
> const char *name)
>
> if (found == -1) {
> error_report("RAMBlock '%s' not found on destination", name);
> + rcu_read_unlock();
> return -ENOENT;
> }
>
> @@ -3502,6 +3615,7 @@ rdma_block_notification_handle(QIOChannelRDMA *rioc,
> const char *name)
> trace_rdma_block_notification_handle(name, rdma->next_src_index);
> rdma->next_src_index++;
>
> + rcu_read_unlock();
> return 0;
> }
>
> @@ -3524,11 +3638,19 @@ static int qemu_rdma_registration_start(QEMUFile *f,
> void *opaque,
> uint64_t flags, void *data)
> {
> QIOChannelRDMA *rioc = QIO_CHANNEL_RDMA(opaque);
> - RDMAContext *rdma = rioc->rdma;
> + RDMAContext *rdma;
> +
> + rcu_read_lock();
> + rdma = atomic_rcu_read(&rioc->rdmaout);
> + if (!rdma) {
> + rcu_read_unlock();
> + return -EIO;
> + }
>
> CHECK_ERROR_STATE();
>
> if (migrate_get_current()->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
> + rcu_read_unlock();
> return 0;
> }
>
> @@ -3536,6 +3658,7 @@ static int qemu_rdma_registration_start(QEMUFile *f,
> void *opaque,
> qemu_put_be64(f, RAM_SAVE_FLAG_HOOK);
> qemu_fflush(f);
>
> + rcu_read_unlock();
> return 0;
> }
>
> @@ -3548,13 +3671,21 @@ static int qemu_rdma_registration_stop(QEMUFile *f,
> void *opaque,
> {
> Error *local_err = NULL, **errp = &local_err;
> QIOChannelRDMA *rioc = QIO_CHANNEL_RDMA(opaque);
> - RDMAContext *rdma = rioc->rdma;
> + RDMAContext *rdma;
> RDMAControlHeader head = { .len = 0, .repeat = 1 };
> int ret = 0;
>
> + rcu_read_lock();
> + rdma = atomic_rcu_read(&rioc->rdmaout);
> + if (!rdma) {
> + rcu_read_unlock();
> + return -EIO;
> + }
> +
> CHECK_ERROR_STATE();
>
> if (migrate_get_current()->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
> + rcu_read_unlock();
> return 0;
> }
>
> @@ -3586,6 +3717,7 @@ static int qemu_rdma_registration_stop(QEMUFile *f,
> void *opaque,
> qemu_rdma_reg_whole_ram_blocks : NULL);
> if (ret < 0) {
> ERROR(errp, "receiving remote info!");
> + rcu_read_unlock();
> return ret;
> }
>
> @@ -3609,6 +3741,7 @@ static int qemu_rdma_registration_stop(QEMUFile *f,
> void *opaque,
> "not identical on both the source and destination.",
> local->nb_blocks, nb_dest_blocks);
> rdma->error_state = -EINVAL;
> + rcu_read_unlock();
> return -EINVAL;
> }
>
> @@ -3625,6 +3758,7 @@ static int qemu_rdma_registration_stop(QEMUFile *f,
> void *opaque,
> local->block[i].length,
> rdma->dest_blocks[i].length);
> rdma->error_state = -EINVAL;
> + rcu_read_unlock();
> return -EINVAL;
> }
> local->block[i].remote_host_addr =
> @@ -3642,9 +3776,11 @@ static int qemu_rdma_registration_stop(QEMUFile *f,
> void *opaque,
> goto err;
> }
>
> + rcu_read_unlock();
> return 0;
> err:
> rdma->error_state = ret;
> + rcu_read_unlock();
> return ret;
> }
>
> @@ -3662,10 +3798,15 @@ static const QEMUFileHooks rdma_write_hooks = {
> static void qio_channel_rdma_finalize(Object *obj)
> {
> QIOChannelRDMA *rioc = QIO_CHANNEL_RDMA(obj);
> - if (rioc->rdma) {
> - qemu_rdma_cleanup(rioc->rdma);
> - g_free(rioc->rdma);
> - rioc->rdma = NULL;
> + if (rioc->rdmain) {
> + qemu_rdma_cleanup(rioc->rdmain);
> + g_free(rioc->rdmain);
> + rioc->rdmain = NULL;
> + }
> + if (rioc->rdmaout) {
> + qemu_rdma_cleanup(rioc->rdmaout);
> + g_free(rioc->rdmaout);
> + rioc->rdmaout = NULL;
> }
> }
>
> @@ -3705,13 +3846,16 @@ static QEMUFile *qemu_fopen_rdma(RDMAContext *rdma,
> const char *mode)
> }
>
> rioc = QIO_CHANNEL_RDMA(object_new(TYPE_QIO_CHANNEL_RDMA));
> - rioc->rdma = rdma;
>
> if (mode[0] == 'w') {
> rioc->file = qemu_fopen_channel_output(QIO_CHANNEL(rioc));
> + rioc->rdmaout = rdma;
> + rioc->rdmain = rdma->return_path;
> qemu_file_set_hooks(rioc->file, &rdma_write_hooks);
> } else {
> rioc->file = qemu_fopen_channel_input(QIO_CHANNEL(rioc));
> + rioc->rdmain = rdma;
> + rioc->rdmaout = rdma->return_path;
> qemu_file_set_hooks(rioc->file, &rdma_read_hooks);
> }
>
> diff --git a/migration/savevm.c b/migration/savevm.c
> index c2f34ff..21c07d4 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -1622,6 +1622,7 @@ static void *postcopy_ram_listen_thread(void *opaque)
> qemu_sem_post(&mis->listen_thread_sem);
> trace_postcopy_ram_listen_thread_start();
>
> + rcu_register_thread();
> /*
> * Because we're a thread and not a coroutine we can't yield
> * in qemu_file, and thus we must be blocking now.
> @@ -1662,6 +1663,7 @@ static void *postcopy_ram_listen_thread(void *opaque)
> * to leave the guest running and fire MCEs for pages that never
> * arrived as a desperate recovery step.
> */
> + rcu_unregister_thread();
> exit(EXIT_FAILURE);
> }
>
> @@ -1676,6 +1678,7 @@ static void *postcopy_ram_listen_thread(void *opaque)
> migration_incoming_state_destroy();
> qemu_loadvm_state_cleanup();
>
> + rcu_unregister_thread();
> return NULL;
> }
>
> --
> 1.8.3.1
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
