Re: [Xen-devel] [PATCH 3 of 9 v2] libxl: add libxl__forkexec function to libxl_exec

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2011-11-18 at 11:59 +0000, Roger Pau Monne wrote:
> # HG changeset patch
> # User Roger Pau Monne <roger.pau@xxxxxxxxxxxxx>
> # Date 1321609614 -3600
> # Node ID ec94a7e4983ad6338db20fa0777a85507b582607
> # Parent  9e8abd626484f82a95d0edc07834ae287bc9467a
> libxl: add libxl__forkexec function to libxl_exec
> 
> Add a new function to libxl_exec that performs a fork and executes
> the passed arguments using libxl__exec.
> 
> Signed-off-by: Roger Pau Monne <roger.pau@xxxxxxxxxxxxx>
> 
> diff -r 9e8abd626484 -r ec94a7e4983a tools/libxl/libxl_exec.c
> --- a/tools/libxl/libxl_exec.c        Fri Sep 30 14:38:55 2011 +0200
> +++ b/tools/libxl/libxl_exec.c        Fri Nov 18 10:46:54 2011 +0100
> @@ -450,6 +450,40 @@ int libxl__spawn_check(libxl__gc *gc, li
>      return ERROR_FAIL;
>  }
>  
> +int libxl__forkexec(libxl__gc *gc, int stdinfd, int stdoutfd,
> +                    int stderrfd, char **args)
> +{
> +    libxl_ctx *ctx = libxl__gc_owner(gc);
> +    int status;
> +    int rc = 0;
> +    pid_t pid = fork();
> +
> +    switch (pid) {
> +    case -1:
> +        LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "fork failed\n");
> +        rc = -1;
> +        break;
> +    case 0:
> +        libxl__exec(stdinfd, stdoutfd, stderrfd, args[0], args);
> +        /* libxl__exec never returns */
> +    default:
> +        while (waitpid(pid, &status, 0) < 0) {
> +            if (errno != EINTR) {
> +                LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "waitpid failed\n");
> +                rc = -1;
> +                break;
> +            }
> +        }
> +        if (WIFEXITED(status)) {
> +            rc = WEXITSTATUS(status);
> +        } else {
> +            rc = -1;
> +        }
> +        break;
> +    }
> +    return rc;
> +}
> +
>  /*
>   * Local variables:
>   * mode: C
> diff -r 9e8abd626484 -r ec94a7e4983a tools/libxl/libxl_internal.h
> --- a/tools/libxl/libxl_internal.h    Fri Sep 30 14:38:55 2011 +0200
> +++ b/tools/libxl/libxl_internal.h    Fri Nov 18 10:46:54 2011 +0100
> @@ -400,6 +400,20 @@ _hidden int libxl__spawn_check(libxl__gc
>  _hidden void libxl__exec(int stdinfd, int stdoutfd, int stderrfd,
>                 const char *arg0, char **args); // logs errors, never returns
>  
> +/*
> + * libxl__forkexec - Executes a file synchronously
> + * gc: allocation pool
> + * stdinfd, stdoutfd, stderrfd: fds to pass to libxl__exec
> + * args: file to execute and arguments to pass in the following format
> + *      args[0]: file to execute
> + *      args[1]: first argument to pass to the called program
> + *      args[n]: nth argument to pass to the called program

args[n] must be NULL, right?

> + *
> + * Returns 0 on success, and < 0 on error.
> + */
> +_hidden int libxl__forkexec(libxl__gc *gc, int stdinfd, int stdoutfd,
> +                            int stderrfd, char **args);
> +
>  /* from xl_create */
>  _hidden int libxl__domain_make(libxl__gc *gc, libxl_domain_create_info 
> *info, uint32_t *domid);
>  _hidden int libxl__domain_build(libxl__gc *gc,
> 
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