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Re: [Qemu-devel] [PATCH v2] qemu-ga: guest-shutdown: use only async-sign
From: |
Michael Roth |
Subject: |
Re: [Qemu-devel] [PATCH v2] qemu-ga: guest-shutdown: use only async-signal-safe functions |
Date: |
Mon, 14 May 2012 17:25:04 -0500 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Mon, May 14, 2012 at 03:25:20PM -0300, Luiz Capitulino wrote:
> POSIX mandates[1] that a child process of a multi-thread program uses
> only async-signal-safe functions before exec(). We consider qemu-ga
> to be multi-thread, because it uses glib.
>
> However, qmp_guest_shutdown() uses functions that are not
> async-signal-safe. Fix it the following way:
>
> - fclose() -> reopen_fd_to_null()
> - execl() -> execle()
> - exit() -> _exit()
> - drop slog() usage (which is not safe)
>
> [1] http://pubs.opengroup.org/onlinepubs/009695399/functions/fork.html
>
> Signed-off-by: Luiz Capitulino <address@hidden>
Thanks, applied to qga branch.
> ---
>
> o v2
>
> - fix doc typo
> - drop 'ret' and use EXIT_FAILURE instead
>
> qapi-schema-guest.json | 3 +--
> qga/commands-posix.c | 19 ++++++++-----------
> 2 files changed, 9 insertions(+), 13 deletions(-)
>
> diff --git a/qapi-schema-guest.json b/qapi-schema-guest.json
> index 1c949ff..bd2256d 100644
> --- a/qapi-schema-guest.json
> +++ b/qapi-schema-guest.json
> @@ -126,8 +126,7 @@
> # @guest-shutdown:
> #
> # Initiate guest-activated shutdown. Note: this is an asynchronous
> -# shutdown request, with no guaruntee of successful shutdown. Errors
> -# will be logged to guest's syslog.
> +# shutdown request, with no guarantee of successful shutdown.
> #
> # @mode: #optional "halt", "powerdown" (default), or "reboot"
> #
> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> index 9a59276..15ce928 100644
> --- a/qga/commands-posix.c
> +++ b/qga/commands-posix.c
> @@ -37,8 +37,8 @@
> void qmp_guest_shutdown(bool has_mode, const char *mode, Error **err)
> {
> const char *shutdown_flag;
> - int ret, status;
> pid_t rpid, pid;
> + int status;
>
> slog("guest-shutdown called, mode: %s", mode);
> if (!has_mode || strcmp(mode, "powerdown") == 0) {
> @@ -57,16 +57,13 @@ void qmp_guest_shutdown(bool has_mode, const char *mode,
> Error **err)
> if (pid == 0) {
> /* child, start the shutdown */
> setsid();
> - fclose(stdin);
> - fclose(stdout);
> - fclose(stderr);
> -
> - ret = execl("/sbin/shutdown", "shutdown", shutdown_flag, "+0",
> - "hypervisor initiated shutdown", (char*)NULL);
> - if (ret) {
> - slog("guest-shutdown failed: %s", strerror(errno));
> - }
> - exit(!!ret);
> + reopen_fd_to_null(0);
> + reopen_fd_to_null(1);
> + reopen_fd_to_null(2);
> +
> + execle("/sbin/shutdown", "shutdown", shutdown_flag, "+0",
> + "hypervisor initiated shutdown", (char*)NULL, environ);
> + _exit(EXIT_FAILURE);
> } else if (pid < 0) {
> goto exit_err;
> }
> --
> 1.7.9.2.384.g4a92a
>