Quoting Chris Wilson (2018-08-30 09:44:33)
> Currently we wrap our fd inside a FILE* stream to make use of vfprintf,
> but the man page leaves the question of errno and signal handling in
> doubt. It is documented as returning a negative value and setting
> ferror(), but we have been interpreting errno to handle signal
> restarting. As that is in doubt, reduce it to a sprintf and reuse our
> common interrupt handling write() that already returns -errno.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Katarzyna Dec <katarzyna.dec@xxxxxxxxx>
> ---
> lib/igt_sysfs.c | 37 ++++++++++++++++++++++++++-----------
> 1 file changed, 26 insertions(+), 11 deletions(-)
>
> diff --git a/lib/igt_sysfs.c b/lib/igt_sysfs.c
> index 8efe889be..b39da4c2a 100644
> --- a/lib/igt_sysfs.c
> +++ b/lib/igt_sysfs.c
> @@ -387,22 +387,37 @@ int igt_sysfs_scanf(int dir, const char *attr, const char *fmt, ...)
>
> int igt_sysfs_vprintf(int dir, const char *attr, const char *fmt, va_list ap)
> {
> - FILE *file;
> - int fd;
> - int ret = -1;
> + char stack[128], *buf = stack;
> + va_list tmp;
> + int ret, fd;
>
> fd = openat(dir, attr, O_WRONLY);
> if (fd < 0)
> - return -1;
> + return -errno;
>
> - file = fdopen(fd, "w");
> - if (file) {
> - do {
> - ret = vfprintf(file, fmt, ap);
> - } while (ret == -1 && errno == EINTR);
> - fclose(file);
> + va_copy(tmp, ap);
> + ret = vsnprintf(buf, sizeof(stack), fmt, tmp);
> + va_end(tmp);
> + if (ret < 0)
> + return -EINVAL;
> +
> + if (ret > sizeof(stack)) {
> + int len = ret + 1;
> +
> + buf = malloc(len);
> + if (!buf)
> + return -ENOMEM;
> +
> + ret = vsnprintf(buf, ret, fmt, ap);
> + if (ret > len) {
> + free(buf);
> + return -EINVAL;
> + }
> }
> - close(fd);
> +
> + ret = writeN(fd, buf, ret);
> + if (buf != stack)
> + free(buf);
+ close(fd);
>
> return ret;
> }
> --
> 2.19.0.rc1
>
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