linux-kernel - Re: [PATCH v3 3/6] Handle EINTR signal interrupts for read, write, open calls

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Date:   Wed, 21 Jun 2017 09:26:23 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Michael Sartain <mikesart@...tmail.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/6] Handle EINTR signal interrupts for read, write,
 open calls

On Wed, 14 Jun 2017 18:27:58 -0600
Michael Sartain <mikesart@...tmail.com> wrote:

> Read/write/open calls weren't handling EINTR in trace-input.c
> 
> This patch uses the standard GNU C TEMP_FAILURE_RETRY macro to handle EINTR
> return values, and updates read/write calls in trace-msg.c to match.

I understand that GNU C gives the TEMP_FAILURE_RETRY() macro, but I
find it really ugly, and takes away from the flow of the code. Perhaps
we should just add our own static inline functions of the same name:

	write_intr(), read_intr(), open_intr()

that does the same thing and use that instead. The inline functions
could even use the TEMP_FAILURE_RETRY(). I just don't want that ugly
name scattered in the .c code.

Thanks!

-- Steve


> 
> Signed-off-by: Michael Sartain <mikesart@...tmail.com>
> ---
>  trace-cmd-local.h | 2 +-
>  trace-input.c     | 8 ++++----
>  trace-msg.c       | 8 ++------
>  3 files changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/trace-cmd-local.h b/trace-cmd-local.h
> index 9412f9d..8595a8a 100644
> --- a/trace-cmd-local.h
> +++ b/trace-cmd-local.h
> @@ -31,7 +31,7 @@ static ssize_t __do_write(int fd, const void *data, size_t size)
>  	ssize_t w;
>  
>  	do {
> -		w = write(fd, data, size - tot);
> +		w = TEMP_FAILURE_RETRY(write(fd, data, size - tot));
>  		tot += w;
>  
>  		if (!w)
> diff --git a/trace-input.c b/trace-input.c
> index 89ddcf5..251d32b 100644
> --- a/trace-input.c
> +++ b/trace-input.c
> @@ -202,7 +202,7 @@ static ssize_t do_read(struct tracecmd_input *handle, void *data, size_t size)
>  	ssize_t r;
>  
>  	do {
> -		r = read(handle->fd, data, size - tot);
> +		r = TEMP_FAILURE_RETRY(read(handle->fd, data, size - tot));
>  		tot += r;
>  
>  		if (!r)
> @@ -774,7 +774,7 @@ static int read_page(struct tracecmd_input *handle, off64_t offset,
>  	off64_t ret;
>  
>  	if (handle->use_pipe) {
> -		ret = read(handle->cpu_data[cpu].pipe_fd, map, handle->page_size);
> +		ret = TEMP_FAILURE_RETRY(read(handle->cpu_data[cpu].pipe_fd, map, handle->page_size));
>  		/* Set EAGAIN if the pipe is empty */
>  		if (ret < 0) {
>  			errno = EAGAIN;
> @@ -2645,7 +2645,7 @@ struct tracecmd_input *tracecmd_alloc(const char *file)
>  {
>  	int fd;
>  
> -	fd = open(file, O_RDONLY);
> +	fd = TEMP_FAILURE_RETRY(open(file, O_RDONLY));
>  	if (fd < 0)
>  		return NULL;
>  
> @@ -2686,7 +2686,7 @@ struct tracecmd_input *tracecmd_open(const char *file)
>  {
>  	int fd;
>  
> -	fd = open(file, O_RDONLY);
> +	fd = TEMP_FAILURE_RETRY(open(file, O_RDONLY));
>  	if (fd < 0)
>  		return NULL;
>  
> diff --git a/trace-msg.c b/trace-msg.c
> index 3991985..d358318 100644
> --- a/trace-msg.c
> +++ b/trace-msg.c
> @@ -291,10 +291,8 @@ static int msg_read(int fd, void *buf, u32 size, int *n)
>  	ssize_t r;
>  
>  	while (size) {
> -		r = read(fd, buf + *n, size);
> +		r = TEMP_FAILURE_RETRY(read(fd, buf + *n, size));
>  		if (r < 0) {
> -			if (errno == EINTR)
> -				continue;
>  			return -errno;
>  		} else if (!r)
>  			return -ENOTCONN;
> @@ -662,10 +660,8 @@ int tracecmd_msg_collect_metadata(int ifd, int ofd)
>  		t = n;
>  		s = 0;
>  		do {
> -			s = write(ofd, msg.data.meta.buf+s, t);
> +			s = TEMP_FAILURE_RETRY(write(ofd, msg.data.meta.buf+s, t));
>  			if (s < 0) {
> -				if (errno == EINTR)
> -					continue;
>  				warning("writing to file");
>  				return -errno;
>  			}