Re: [PATCH 3/8] trans/mtab: properly lock mtab objects

[Samuel Thibault]

Ack

Justus Winter, le Sun 12 Jan 2014 20:08:40 +0100, a écrit :
> * trans/mtab.c (struct mtab): Add lock.
> (open_hook): Initialize lock.
> (close_hook): Destroy lock.
> (trivfs_S_io_read): Lock mtab object, adjust error handling accordingly.
> (trivfs_S_io_seek): Likewise.
> (trivfs_S_io_readable): Likewise.
> ---
>  trans/mtab.c | 44 ++++++++++++++++++++++++++++++++------------
>  1 file changed, 32 insertions(+), 12 deletions(-)
> 
> diff --git a/trans/mtab.c b/trans/mtab.c
> index 0bcd52b..5a5a07d 100644
> --- a/trans/mtab.c
> +++ b/trans/mtab.c
> @@ -27,6 +27,7 @@
>  #include <hurd/trivfs.h>
>  #include <inttypes.h>
>  #include <mntent.h>
> +#include <pthread.h>
>  #include <stdlib.h>
>  #include <stdio.h>
>  #include <string.h>
> @@ -47,6 +48,7 @@ struct trivfs_control *control;
>     They keep track of the content and file position of the client.  */
>  struct mtab
>  {
> +  pthread_mutex_t lock;
>    char *contents;
>    size_t contents_len;
>    off_t offs;
> @@ -569,6 +571,7 @@ open_hook (struct trivfs_peropen *peropen)
>    peropen->hook = mtab;
>  
>    /* Initialize the fields.  */
> +  pthread_mutex_init (&mtab->lock, NULL);
>    mtab->offs = 0;
>    mtab->contents = NULL;
>    mtab->contents_len = 0;
> @@ -602,8 +605,10 @@ open_hook (struct trivfs_peropen *peropen)
>  static void
>  close_hook (struct trivfs_peropen *peropen)
>  {
> -  free (((struct mtab *) peropen->hook)->contents);
> -  free (peropen->hook);
> +  struct mtab *op = peropen->hook;
> +  pthread_mutex_destroy (&op->lock);
> +  free (op->contents);
> +  free (op);
>  }
>  
>  /* Read data from an IO object.       If offset is -1, read from the object
> @@ -615,6 +620,7 @@ trivfs_S_io_read (struct trivfs_protid *cred,
>                 char **data, mach_msg_type_number_t *data_len,
>                 loff_t offs, mach_msg_type_number_t amount)
>  {
> +  error_t err = 0;
>    struct mtab *op;
>  
>    /* Deny access if they have bad credentials.       */
> @@ -626,12 +632,13 @@ trivfs_S_io_read (struct trivfs_protid *cred,
>  
>    /* Get the offset.  */
>    op = cred->po->hook;
> +  pthread_mutex_lock (&op->lock);
>  
>    if (op->contents == NULL)
>      {
> -      error_t err = mtab_populate (op, target_path, insecure);
> +      err = mtab_populate (op, target_path, insecure);
>        if (err)
> -        return err;
> +     goto out;
>      }
>  
>    if (offs == -1)
> @@ -650,7 +657,10 @@ trivfs_S_io_read (struct trivfs_protid *cred,
>       {
>         *data = mmap (0, amount, PROT_READ|PROT_WRITE, MAP_ANON, 0, 0);
>         if (*data == MAP_FAILED)
> -         return ENOMEM;
> +         {
> +           err = ENOMEM;
> +           goto out;
> +         }
>       }
>  
>        /* Copy the constant data into the buffer.  */
> @@ -661,7 +671,9 @@ trivfs_S_io_read (struct trivfs_protid *cred,
>      }
>  
>    *data_len = amount;
> -  return 0;
> + out:
> +  pthread_mutex_unlock (&op->lock);
> +  return err;
>  }
>  
>  
> @@ -671,16 +683,18 @@ trivfs_S_io_seek (struct trivfs_protid *cred,
>                 mach_port_t reply, mach_msg_type_name_t reply_type,
>                 off_t offs, int whence, off_t *new_offs)
>  {
> +  error_t err = 0;
>    if (! cred)
>      return EOPNOTSUPP;
>  
>    struct mtab *op = cred->po->hook;
> +  pthread_mutex_lock (&op->lock);
>  
>    if (op->contents == NULL)
>      {
> -      error_t err = mtab_populate (op, target_path, insecure);
> +      err = mtab_populate (op, target_path, insecure);
>        if (err)
> -        return err;
> +     goto out;
>      }
>  
>    switch (whence)
> @@ -698,10 +712,12 @@ trivfs_S_io_seek (struct trivfs_protid *cred,
>         break;
>       }
>      default:
> -      return EINVAL;
> +      err = EINVAL;
>      }
>  
> -  return 0;
> + out:
> +  pthread_mutex_unlock (&op->lock);
> +  return err;
>  }
>  
>  /* If this variable is set, it is called every time a new peropen
> @@ -720,6 +736,7 @@ trivfs_S_io_readable (struct trivfs_protid *cred,
>                     mach_port_t reply, mach_msg_type_name_t replytype,
>                     mach_msg_type_number_t *amount)
>  {
> +  error_t err = 0;
>    if (!cred)
>      return EOPNOTSUPP;
>  
> @@ -727,16 +744,19 @@ trivfs_S_io_readable (struct trivfs_protid *cred,
>      return EINVAL;
>  
>    struct mtab *op = cred->po->hook;
> +  pthread_mutex_lock (&op->lock);
>  
>    if (op->contents == NULL)
>      {
>        error_t err = mtab_populate (op, target_path, insecure);
>        if (err)
> -        return err;
> +     goto out;
>      }
>  
>    *amount = op->contents_len - op->offs;
> -  return 0;
> + out:
> +  pthread_mutex_unlock (&op->lock);
> +  return err;
>  }
>  
>  /* SELECT_TYPE is the bitwise OR of SELECT_READ, SELECT_WRITE, and 
> SELECT_URG.
> -- 
> 1.8.5.2
> 

-- 
Samuel
<N> je déteste import
<N> parce que lorsque tu fais du python et que tu oublies le #!/bin/env python 
et que tu mets le fichier exécutable
<N> import est exécuté
 -+- #ens-mim - pourquoi mon script python change le curseur de la souris ?! -+-