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Re: [Qemu-devel] Re: [PATCH 2/4] migration-tcp: threaded tcp incoming mi


From: Anthony Liguori
Subject: Re: [Qemu-devel] Re: [PATCH 2/4] migration-tcp: threaded tcp incoming migration.
Date: Tue, 01 Jun 2010 11:28:39 -0500
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100423 Lightning/1.0b1 Thunderbird/3.0.4

On 06/01/2010 11:23 AM, Yoshiaki Tamura wrote:
2010/6/2 Anthony Liguori<address@hidden>:
On 06/01/2010 10:40 AM, Yoshiaki Tamura wrote:
Create a thread to handle tcp incoming migration when CONFIG_IOTHREAD
is enabled.  Spawned thread writes it's return status to th_fds[1]
before exit, and main thread joins and reads it.  In
tcp_start_incoming_migration(), allocate FdMigrationState and return
MigrationState to let migration to print incoming migration info.

In the absence of any locking, I can't see how this is safe.
Right.  If we use threading here, we need to prevent commands from
monitor that affects incoming thread.

There's a huge number of calls that can get made during live migration that can also be triggered by the monitor.

Even the basic things likes qemu_set_fd_handler2 can cause havoc.

Just preventing certain monitor commands is not sufficient.

Regards,

Anthony Liguori

Thanks,

Yoshi

Regards,

Anthony Liguori

Signed-off-by: Yoshiaki Tamura<address@hidden>
---
  migration-tcp.c |   86
++++++++++++++++++++++++++++++++++++++++++++++---------
  migration.h     |    2 +-
  2 files changed, 73 insertions(+), 15 deletions(-)

diff --git a/migration-tcp.c b/migration-tcp.c
index 95ce722..f20e5fe 100644
--- a/migration-tcp.c
+++ b/migration-tcp.c
@@ -18,6 +18,7 @@
  #include "sysemu.h"
  #include "buffered_file.h"
  #include "block.h"
+#include "qemu-thread.h"

  //#define DEBUG_MIGRATION_TCP

@@ -29,6 +30,11 @@
      do { } while (0)
  #endif

+#ifdef CONFIG_IOTHREAD
+static QemuThread migration_thread;
+static int th_fds[2];
+#endif
+
  static int socket_errno(FdMigrationState *s)
  {
      return socket_error();
@@ -176,41 +182,93 @@ static void tcp_accept_incoming_migration(void
*opaque)
  out_fopen:
      qemu_fclose(f);
  out:
+#ifndef CONFIG_IOTHREAD
      qemu_set_fd_handler2(s, NULL, NULL, NULL, NULL);
+#endif
      close(s);
      close(c);
+#ifdef CONFIG_IOTHREAD
+    write(th_fds[1],&ret, sizeof(ret));
+    qemu_thread_exit(NULL);
+#endif
+}
+
+#ifdef CONFIG_IOTHREAD
+static void tcp_incoming_migration_complete(void *opaque)
+{
+    int ret, state = 0;
+    FdMigrationState *s = opaque;
+
+    qemu_thread_join(&migration_thread, NULL);
+
+    ret = read(th_fds[0],&state, sizeof(state));
+    if (ret == -1) {
+        fprintf(stderr, "failed to read from pipe\n");
+        goto err;
+    }
+
+    s->state = state<    0 ? MIG_STATE_ERROR : MIG_STATE_COMPLETED;
+
+err:
+    qemu_set_fd_handler2(th_fds[0], NULL, NULL, NULL, NULL);
+    close(th_fds[0]);
+    close(th_fds[1]);
  }
+#endif

-int tcp_start_incoming_migration(const char *host_port)
+MigrationState *tcp_start_incoming_migration(const char *host_port)
  {
      struct sockaddr_in addr;
+    FdMigrationState *s;
      int val;
-    int s;

      if (parse_host_port(&addr, host_port)<    0) {
          fprintf(stderr, "invalid host/port combination: %s\n",
host_port);
-        return -EINVAL;
+        return NULL;
      }

-    s = qemu_socket(PF_INET, SOCK_STREAM, 0);
-    if (s == -1)
-        return -socket_error();
+    s = qemu_mallocz(sizeof(*s));
+
+    s->get_error = socket_errno;
+    s->close = tcp_close;
+    s->mig_state.cancel = migrate_fd_cancel;
+    s->mig_state.get_status = migrate_fd_get_status;
+    s->state = MIG_STATE_ACTIVE;
+
+    s->fd = qemu_socket(PF_INET, SOCK_STREAM, 0);
+    if (s->fd == -1) {
+        qemu_free(s);
+        return NULL;
+    }

      val = 1;
-    setsockopt(s, SOL_SOCKET, SO_REUSEADDR, (const char *)&val,
sizeof(val));
+    setsockopt(s->fd, SOL_SOCKET, SO_REUSEADDR,
+               (const char *)&val, sizeof(val));

-    if (bind(s, (struct sockaddr *)&addr, sizeof(addr)) == -1)
+    if (bind(s->fd, (struct sockaddr *)&addr, sizeof(addr)) == -1)
          goto err;

-    if (listen(s, 1) == -1)
+    if (listen(s->fd, 1) == -1)
          goto err;

-    qemu_set_fd_handler2(s, NULL, tcp_accept_incoming_migration, NULL,
-                         (void *)(unsigned long)s);
+#ifdef CONFIG_IOTHREAD
+    if (qemu_pipe(th_fds) == -1) {
+        fprintf(stderr, "failed to create pipe\n");
+        goto err;
+    }

-    return 0;
+    qemu_thread_create(&migration_thread, (void
*)tcp_accept_incoming_migration,
+                       (void *)(unsigned long)s->fd);
+    qemu_set_fd_handler2(th_fds[0], NULL,
tcp_incoming_migration_complete, NULL,
+                         (void *)s);
+#else
+    qemu_set_fd_handler2(s->fd, NULL, tcp_accept_incoming_migration,
NULL,
+                         (void *)(unsigned long)s->fd);
+#endif
+
+    return&s->mig_state;

  err:
-    close(s);
-    return -socket_error();
+    close(s->fd);
+    return NULL;
  }
diff --git a/migration.h b/migration.h
index 385423f..c11e6db 100644
--- a/migration.h
+++ b/migration.h
@@ -76,7 +76,7 @@ MigrationState *exec_start_outgoing_migration(Monitor
*mon,
                                              int blk,
                                              int inc);

-int tcp_start_incoming_migration(const char *host_port);
+MigrationState *tcp_start_incoming_migration(const char *host_port);

  MigrationState *tcp_start_outgoing_migration(Monitor *mon,
                                               const char *host_port,







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