Re: [Qemu-devel] [PATCH 04/14] buffered_file: Move from using a timer to use a thread

[Paolo Bonzini <pbonzini@redhat.com>]

Il 21/09/2012 16:08, Juan Quintela ha scritto:
> We still protect everything except the wait with the iothread lock.
> But we moved from a timer to a thread.  Steps one by one.
> 
> We also need to detect when we have finished with a variable "complete".
> 
> Signed-off-by: Juan Quintela <quintela@redhat.com>
> ---
>  buffered_file.c | 58 +++++++++++++++++++++++++++++++++++----------------------
>  1 file changed, 36 insertions(+), 22 deletions(-)
> 
> diff --git a/buffered_file.c b/buffered_file.c
> index 318d0f0..61985a9 100644
> --- a/buffered_file.c
> +++ b/buffered_file.c
> @@ -18,6 +18,7 @@
>  #include "qemu-timer.h"
>  #include "qemu-char.h"
>  #include "buffered_file.h"
> +#include "qemu-thread.h"
> 
>  //#define DEBUG_BUFFERED_FILE
> 
> @@ -31,7 +32,8 @@ typedef struct QEMUFileBuffered
>      uint8_t *buffer;
>      size_t buffer_size;
>      size_t buffer_capacity;
> -    QEMUTimer *timer;
> +    QemuThread thread;
> +    bool complete;
>  } QEMUFileBuffered;
> 
>  #ifdef DEBUG_BUFFERED_FILE
> @@ -159,11 +161,8 @@ static int buffered_close(void *opaque)
>      if (ret >= 0) {
>          ret = ret2;
>      }
> -    qemu_del_timer(s->timer);
> -    qemu_free_timer(s->timer);
> -    g_free(s->buffer);
> -    g_free(s);
> -
> +    ret = migrate_fd_close(s->migration_state);
> +    s->complete = true;
>      return ret;
>  }
> 
> @@ -214,23 +213,38 @@ static int64_t buffered_get_rate_limit(void *opaque)
>      return s->xfer_limit;
>  }
> 
> -static void buffered_rate_tick(void *opaque)
> +/* 10ms  xfer_limit is the limit that we should write each 10ms */
> +#define BUFFER_DELAY 100
> +
> +static void *buffered_file_thread(void *opaque)
>  {
>      QEMUFileBuffered *s = opaque;
> +    int64_t expire_time = qemu_get_clock_ms(rt_clock) + BUFFER_DELAY;
> 
> -    if (qemu_file_get_error(s->file)) {
> -        buffered_close(s);
> -        return;
> -    }
> -
> -    qemu_mod_timer(s->timer, qemu_get_clock_ms(rt_clock) + 100);
> -
> -    if (s->freeze_output)
> -        return;
> -
> -    s->bytes_xfer = 0;
> +    while (true) {
> +        int64_t current_time = qemu_get_clock_ms(rt_clock);
> 
> -    buffered_put_buffer(s, NULL, 0, 0);
> +        if (s->complete) {
> +            break;
> +        }
> +        if (s->freeze_output) {
> +            continue;
> +        }
> +        if (current_time >= expire_time) {
> +            s->bytes_xfer = 0;
> +            expire_time = current_time + BUFFER_DELAY;
> +        }
> +        if (s->bytes_xfer >= s->xfer_limit) {
> +            /* usleep expects microseconds */
> +            usleep((expire_time - current_time)*1000);

usleep is broken under IIRC Solaris (it uses signals and conflicts with
qemu-timer.c).  Please use g_usleep instead.

Bonus points for converting other users (hw/xenfb.c, qemu-ga.c,
tests/test-iov.c).

> +        }
> +        qemu_mutex_lock_iothread();
> +        buffered_put_buffer(s, NULL, 0, 0);
> +        qemu_mutex_unlock_iothread();
> +    }
> +    g_free(s->buffer);
> +    g_free(s);

I think freeing "s" here is incorrect.  Instead, you should "join" the
thread after setting s->complete = true, and move the g_free(s) to
buffered_close.

> +    return NULL;
>  }
> 
>  QEMUFile *qemu_fopen_ops_buffered(MigrationState *migration_state)
> @@ -241,15 +255,15 @@ QEMUFile *qemu_fopen_ops_buffered(MigrationState *migration_state)
> 
>      s->migration_state = migration_state;
>      s->xfer_limit = migration_state->bandwidth_limit / 10;
> +    s->complete = false;
> 
>      s->file = qemu_fopen_ops(s, buffered_put_buffer, NULL,
>                               buffered_close, buffered_rate_limit,
>                               buffered_set_rate_limit,
>  			     buffered_get_rate_limit);
> 
> -    s->timer = qemu_new_timer_ms(rt_clock, buffered_rate_tick, s);
> -
> -    qemu_mod_timer(s->timer, qemu_get_clock_ms(rt_clock) + 100);
> +    qemu_thread_create(&s->thread, buffered_file_thread, s,
> +                       QEMU_THREAD_DETACHED);

So this needs to become QEMU_THREAD_JOINABLE.

> 
>      return s->file;
>  }
> 

Paolo