Re: [PATCH v2 1/2] Refactoring: refactor TFR() macro to RETRY_ON_EINTR()

[Christian Schoenebeck <qemu_oss@crudebyte.com>]

On Mittwoch, 12. Oktober 2022 14:28:23 CEST Nikita Ivanov wrote:
> Rename macro name to more transparent one and refactor
> it to expression.
> 
> Signed-off-by: Nikita Ivanov <nivanov@cloudlinux.com>
> ---
>  chardev/char-fd.c    | 2 +-
>  chardev/char-pipe.c  | 8 +++++---
>  include/qemu/osdep.h | 8 +++++++-
>  net/tap-bsd.c        | 6 +++---
>  net/tap-linux.c      | 2 +-
>  net/tap-solaris.c    | 8 ++++----
>  os-posix.c           | 2 +-
>  7 files changed, 22 insertions(+), 14 deletions(-)
> 
> diff --git a/chardev/char-fd.c b/chardev/char-fd.c
> index cf78454841..d2c4923359 100644
> --- a/chardev/char-fd.c
> +++ b/chardev/char-fd.c
> @@ -198,7 +198,7 @@ int qmp_chardev_open_file_source(char *src, int flags,
> Error **errp)
>  {
>      int fd = -1;
> 
> -    TFR(fd = qemu_open_old(src, flags, 0666));
> +    fd = RETRY_ON_EINTR(qemu_open_old(src, flags, 0666));
>      if (fd == -1) {
>          error_setg_file_open(errp, errno, src);
>      }
> diff --git a/chardev/char-pipe.c b/chardev/char-pipe.c
> index 66d3b85091..5ad30bcc59 100644
> --- a/chardev/char-pipe.c
> +++ b/chardev/char-pipe.c
> @@ -131,8 +131,8 @@ static void qemu_chr_open_pipe(Chardev *chr,
> 
>      filename_in = g_strdup_printf("%s.in", filename);
>      filename_out = g_strdup_printf("%s.out", filename);
> -    TFR(fd_in = qemu_open_old(filename_in, O_RDWR | O_BINARY));
> -    TFR(fd_out = qemu_open_old(filename_out, O_RDWR | O_BINARY));
> +    fd_in = RETRY_ON_EINTR(qemu_open_old(filename_in, O_RDWR | O_BINARY));
> +    fd_out = RETRY_ON_EINTR(qemu_open_old(filename_out, O_RDWR |
> O_BINARY));
>      g_free(filename_in);
>      g_free(filename_out);
>      if (fd_in < 0 || fd_out < 0) {
> @@ -142,7 +142,9 @@ static void qemu_chr_open_pipe(Chardev *chr,
>          if (fd_out >= 0) {
>              close(fd_out);
>          }
> -        TFR(fd_in = fd_out = qemu_open_old(filename, O_RDWR | O_BINARY));
> +        fd_in = fd_out = RETRY_ON_EINTR(
> +            qemu_open_old(filename, O_RDWR | O_BINARY)
> +        );
>          if (fd_in < 0) {
>              error_setg_file_open(errp, errno, filename);
>              return;
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index b1c161c035..a470905475 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -243,7 +243,13 @@ void QEMU_ERROR("code path is reachable")
>  #define ESHUTDOWN 4099
>  #endif
> 
> -#define TFR(expr) do { if ((expr) != -1) break; } while (errno == EINTR)
> +#define RETRY_ON_EINTR(expr) \
> +    (__extension__                                          \
> +        ({ typeof(expr) __result;                               \
> +           do {                                             \
> +                __result = (typeof(expr)) (expr);         \

Not a big deal, but as Peter already pointed out in previous version: you 
could drop the type cast in this particular form here.

glibc's TEMP_FAILURE_RETRY() version needs the cast as it uses `long int` as 
hard coded type for the result variable, whereas this version here uses a 
generic approach by declaring the result variable already exactly with the 
type the passed expression evaluates to, so the cast is redundant in this 
version here.

> +           } while (__result == -1L && errno == EINTR);     \
> +           __result; }))
> 
>  /* time_t may be either 32 or 64 bits depending on the host OS, and
>   * can be either signed or unsigned, so we can't just hardcode a
> diff --git a/net/tap-bsd.c b/net/tap-bsd.c
> index 005ce05c6e..4c98fdd337 100644
> --- a/net/tap-bsd.c
> +++ b/net/tap-bsd.c
> @@ -56,7 +56,7 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr,
> } else {
>              snprintf(dname, sizeof dname, "/dev/tap%d", i);
>          }
> -        TFR(fd = open(dname, O_RDWR));
> +        fd = RETRY_ON_EINTR(open(dname, O_RDWR));
>          if (fd >= 0) {
>              break;
>          }
> @@ -111,7 +111,7 @@ static int tap_open_clone(char *ifname, int
> ifname_size, Error **errp)
>      int fd, s, ret;
>      struct ifreq ifr;
> 
> -    TFR(fd = open(PATH_NET_TAP, O_RDWR));
> +    fd = RETRY_ON_EINTR(open(PATH_NET_TAP, O_RDWR));
>      if (fd < 0) {
>          error_setg_errno(errp, errno, "could not open %s", PATH_NET_TAP);
>          return -1;
> @@ -159,7 +159,7 @@ int tap_open(char *ifname, int ifname_size, int
> *vnet_hdr,
>      if (ifname[0] != '\0') {
>          char dname[100];
>          snprintf(dname, sizeof dname, "/dev/%s", ifname);
> -        TFR(fd = open(dname, O_RDWR));
> +        fd = RETRY_ON_EINTR(open(dname, O_RDWR));
>          if (fd < 0 && errno != ENOENT) {
>              error_setg_errno(errp, errno, "could not open %s", dname);
>              return -1;
> diff --git a/net/tap-linux.c b/net/tap-linux.c
> index 304ff45071..f54f308d35 100644
> --- a/net/tap-linux.c
> +++ b/net/tap-linux.c
> @@ -45,7 +45,7 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr,
> int len = sizeof(struct virtio_net_hdr);
>      unsigned int features;
> 
> -    TFR(fd = open(PATH_NET_TUN, O_RDWR));
> +    fd = RETRY_ON_EINTR(open(PATH_NET_TUN, O_RDWR));
>      if (fd < 0) {
>          error_setg_errno(errp, errno, "could not open %s", PATH_NET_TUN);
>          return -1;
> diff --git a/net/tap-solaris.c b/net/tap-solaris.c
> index a44f8805c2..38e15028bf 100644
> --- a/net/tap-solaris.c
> +++ b/net/tap-solaris.c
> @@ -84,13 +84,13 @@ static int tap_alloc(char *dev, size_t dev_size, Error
> **errp)
>      if( ip_fd )
>         close(ip_fd);
> 
> -    TFR(ip_fd = open("/dev/udp", O_RDWR, 0));
> +    ip_fd = RETRY_ON_EINTR(open("/dev/udp", O_RDWR, 0));
>      if (ip_fd < 0) {
>          error_setg(errp, "Can't open /dev/ip (actually /dev/udp)");
>          return -1;
>      }
> 
> -    TFR(tap_fd = open("/dev/tap", O_RDWR, 0));
> +    tap_fd = RETRY_ON_EINTR(open("/dev/tap", O_RDWR, 0));
>      if (tap_fd < 0) {
>          error_setg(errp, "Can't open /dev/tap");
>          return -1;
> @@ -104,7 +104,7 @@ static int tap_alloc(char *dev, size_t dev_size, Error
> **errp)
>      if ((ppa = ioctl (tap_fd, I_STR, &strioc_ppa)) < 0)
>          error_report("Can't assign new interface");
> 
> -    TFR(if_fd = open("/dev/tap", O_RDWR, 0));
> +    if_fd = RETRY_ON_EINTR(open("/dev/tap", O_RDWR, 0));
>      if (if_fd < 0) {
>          error_setg(errp, "Can't open /dev/tap (2)");
>          return -1;
> @@ -137,7 +137,7 @@ static int tap_alloc(char *dev, size_t dev_size, Error
> **errp)
>      if (ioctl (ip_fd, I_PUSH, "arp") < 0)
>          error_report("Can't push ARP module (3)");
>      /* Open arp_fd */
> -    TFR(arp_fd = open ("/dev/tap", O_RDWR, 0));
> +    arp_fd = RETRY_ON_EINTR(open("/dev/tap", O_RDWR, 0));
>      if (arp_fd < 0)
>          error_report("Can't open %s", "/dev/tap");
> 
> diff --git a/os-posix.c b/os-posix.c
> index 321fc4bd13..bb27f67bac 100644
> --- a/os-posix.c
> +++ b/os-posix.c
> @@ -266,7 +266,7 @@ void os_setup_post(void)
>              error_report("not able to chdir to /: %s", strerror(errno));
>              exit(1);
>          }
> -        TFR(fd = qemu_open_old("/dev/null", O_RDWR));
> +        fd = RETRY_ON_EINTR(qemu_open_old("/dev/null", O_RDWR));
>          if (fd == -1) {
>              exit(1);
>          }
> --
> 2.37.3