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Date:	Sat, 21 May 2016 17:28:58 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Peter Meerwald-Stadler <pmeerw@...erw.net>,
	Crestez Dan Leonard <leonard.crestez@...el.com>
Cc:	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
	Hartmut Knaack <knaack.h@....de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Daniel Baluta <daniel.baluta@...el.com>
Subject: Re: [PATCH 1/2] iio: generic_buffer: Cleanup when receiving signals

On 20/05/16 16:55, Peter Meerwald-Stadler wrote:
> 
>> This also drops all the code freeing string buffers at the end of main.
>> Memory is freed when the process exits anyway so there's no point in
>> cluttering the code with all those gotos.
> 
> well, it helps to see that all memory has been released when looking for 
> leaks :)
> e.g. valgrind becomes much less useful when the program exits with tons of 
> memory still allocated
Beyond that we are looking at code here that will get cut and paste into other
peoples applications - they might not pick up that it doesn't clean up properly
after itself.

I'd much prefer to keep these explicit frees in place.

Jonathan
> 
> functions and global variables could be static
> 
>> ---
>>  tools/iio/generic_buffer.c | 162 ++++++++++++++++++++++++---------------------
>>  1 file changed, 88 insertions(+), 74 deletions(-)
>>
>> diff --git a/tools/iio/generic_buffer.c b/tools/iio/generic_buffer.c
>> index 2429c78..e7bf477 100644
>> --- a/tools/iio/generic_buffer.c
>> +++ b/tools/iio/generic_buffer.c
>> @@ -32,6 +32,8 @@
>>  #include <endian.h>
>>  #include <getopt.h>
>>  #include <inttypes.h>
>> +#include <stdbool.h>
>> +#include <signal.h>
>>  #include "iio_utils.h"
>>  
>>  /**
>> @@ -254,6 +256,69 @@ void print_usage(void)
>>  		"  -w <n>     Set delay between reads in us (event-less mode)\n");
>>  }
>>  
>> +enum autochan autochannels = AUTOCHANNELS_DISABLED;
>> +char *dev_dir_name = NULL;
>> +char *buf_dir_name = NULL;
>> +bool current_trigger_set = false;
>> +
>> +void cleanup(void)
>> +{
>> +	int ret;
>> +
>> +	fprintf(stderr, "Cleanup\n");
>> +
>> +	/* Disable trigger */
>> +	if (dev_dir_name && current_trigger_set) {
>> +		/* Disconnect the trigger - just write a dummy name. */
>> +		ret = write_sysfs_string("trigger/current_trigger",
>> +					 dev_dir_name, "NULL");
>> +		if (ret < 0)
>> +			fprintf(stderr, "Failed to disable trigger: %s\n",
>> +				strerror(-ret));
>> +	}
>> +
>> +	/* Disable buffer */
>> +	if (buf_dir_name) {
>> +		ret = write_sysfs_int("enable", buf_dir_name, 0);
>> +		if (ret < 0)
>> +			fprintf(stderr, "Failed to disable buffer: %s\n",
>> +				strerror(-ret));
>> +	}
>> +
>> +	/* Disable channels if auto-enabled */
>> +	if (dev_dir_name && autochannels == AUTOCHANNELS_ACTIVE) {
>> +		ret = enable_disable_all_channels(dev_dir_name, 0);
>> +		if (ret)
>> +			fprintf(stderr, "Failed to disable all channels\n");
>> +	}
>> +}
>> +
>> +void sig_handler(int signum)
>> +{
>> +	fprintf(stderr, "Caught signal %d\n", signum);
>> +	exit(-signum);
>> +}
>> +
>> +void register_cleanup(void)
>> +{
>> +	struct sigaction sa = { .sa_handler = sig_handler };
>> +	const int signums[] = { SIGINT, SIGTERM, SIGABRT };
>> +	int ret, i;
>> +
>> +	ret = atexit(cleanup);
>> +	if (ret) {
>> +		perror("Failed to register atexit");
>> +		exit(-1);
>> +	}
>> +	for (i = 0; i < ARRAY_SIZE(signums); ++i) {
>> +		ret = sigaction(signums[i], &sa, NULL);
>> +		if (ret) {
>> +			perror("Failed to register signal handler");
>> +			exit(-1);
>> +		}
>> +	}
>> +}
>> +
>>  int main(int argc, char **argv)
>>  {
>>  	unsigned long num_loops = 2;
>> @@ -265,9 +330,7 @@ int main(int argc, char **argv)
>>  
>>  	int num_channels;
>>  	char *trigger_name = NULL, *device_name = NULL;
>> -	char *dev_dir_name, *buf_dir_name;
>>  
>> -	int datardytrigger = 1;
>>  	char *data;
>>  	ssize_t read_size;
>>  	int dev_num, trig_num;
>> @@ -275,11 +338,12 @@ int main(int argc, char **argv)
>>  	int scan_size;
>>  	int noevents = 0;
>>  	int notrigger = 0;
>> -	enum autochan autochannels = AUTOCHANNELS_DISABLED;
>>  	char *dummy;
>>  
>>  	struct iio_channel_info *channels;
>>  
>> +	register_cleanup();
>> +
>>  	while ((c = getopt(argc, argv, "ac:egl:n:t:w:")) != -1) {
>>  		switch (c) {
>>  		case 'a':
>> @@ -310,7 +374,6 @@ int main(int argc, char **argv)
>>  			break;
>>  		case 't':
>>  			trigger_name = optarg;
>> -			datardytrigger = 0;
>>  			break;
>>  		case 'w':
>>  			errno = 0;
>> @@ -352,10 +415,8 @@ int main(int argc, char **argv)
>>  			 */
>>  			ret = asprintf(&trigger_name,
>>  				       "%s-dev%d", device_name, dev_num);
>> -			if (ret < 0) {
>> -				ret = -ENOMEM;
>> -				goto error_free_dev_dir_name;
>> -			}
>> +			if (ret < 0)
>> +				return -ENOMEM;
>>  		}
>>  
>>  		/* Look for this "-devN" trigger */
>> @@ -365,18 +426,15 @@ int main(int argc, char **argv)
>>  			free(trigger_name);
>>  			ret = asprintf(&trigger_name,
>>  				       "%s-trigger", device_name);
>> -			if (ret < 0) {
>> -				ret = -ENOMEM;
>> -				goto error_free_dev_dir_name;
>> -			}
>> +			if (ret < 0)
>> +				return -ENOMEM;
>>  		}
>>  
>>  		trig_num = find_type_by_name(trigger_name, "trigger");
>>  		if (trig_num < 0) {
>>  			fprintf(stderr, "Failed to find the trigger %s\n",
>>  				trigger_name);
>> -			ret = trig_num;
>> -			goto error_free_triggername;
>> +			return trig_num;
>>  		}
>>  
>>  		printf("iio trigger number being used is %d\n", trig_num);
>> @@ -392,7 +450,7 @@ int main(int argc, char **argv)
>>  	if (ret) {
>>  		fprintf(stderr, "Problem reading scan element information\n"
>>  			"diag %s\n", dev_dir_name);
>> -		goto error_free_triggername;
>> +		return ret;
>>  	}
>>  	if (num_channels && autochannels == AUTOCHANNELS_ENABLED) {
>>  		fprintf(stderr, "Auto-channels selected but some channels "
>> @@ -407,7 +465,7 @@ int main(int argc, char **argv)
>>  		ret = enable_disable_all_channels(dev_dir_name, 1);
>>  		if (ret) {
>>  			fprintf(stderr, "Failed to enable all channels\n");
>> -			goto error_free_triggername;
>> +			return ret;
>>  		}
>>  
>>  		/* This flags that we need to disable the channels again */
>> @@ -419,12 +477,12 @@ int main(int argc, char **argv)
>>  			fprintf(stderr, "Problem reading scan element "
>>  				"information\n"
>>  				"diag %s\n", dev_dir_name);
>> -			goto error_disable_channels;
>> +		        return ret;
>>  		}
>>  		if (!num_channels) {
>>  			fprintf(stderr, "Still no channels after "
>>  				"auto-enabling, giving up\n");
>> -			goto error_disable_channels;
>> +		        return ret;
>>  		}
>>  	}
>>  
>> @@ -435,8 +493,7 @@ int main(int argc, char **argv)
>>  			FORMAT_SCAN_ELEMENTS_DIR
>>  			"/*_en or pass -a to autoenable channels and "
>>  			"try again.\n", dev_dir_name);
>> -		ret = -ENOENT;
>> -		goto error_free_triggername;
>> +		return -ENOENT;
>>  	}
>>  
>>  	/*
>> @@ -446,10 +503,8 @@ int main(int argc, char **argv)
>>  	 */
>>  	ret = asprintf(&buf_dir_name,
>>  		       "%siio:device%d/buffer", iio_dir, dev_num);
>> -	if (ret < 0) {
>> -		ret = -ENOMEM;
>> -		goto error_free_channels;
>> -	}
>> +	if (ret < 0)
>> +		return -ENOMEM;
>>  
>>  	if (!notrigger) {
>>  		printf("%s %s\n", dev_dir_name, trigger_name);
>> @@ -463,34 +518,35 @@ int main(int argc, char **argv)
>>  		if (ret < 0) {
>>  			fprintf(stderr,
>>  				"Failed to write current_trigger file\n");
>> -			goto error_free_buf_dir_name;
>> +			return ret;
>>  		}
>> +		current_trigger_set = true;
>>  	}
>>  
>>  	/* Setup ring buffer parameters */
>>  	ret = write_sysfs_int("length", buf_dir_name, buf_len);
>>  	if (ret < 0)
>> -		goto error_free_buf_dir_name;
>> +		return ret;
>>  
>>  	/* Enable the buffer */
>>  	ret = write_sysfs_int("enable", buf_dir_name, 1);
>>  	if (ret < 0) {
>>  		fprintf(stderr,
>>  			"Failed to enable buffer: %s\n", strerror(-ret));
>> -		goto error_free_buf_dir_name;
>> +		return ret;
>>  	}
>>  
>>  	scan_size = size_from_channelarray(channels, num_channels);
>>  	data = malloc(scan_size * buf_len);
>>  	if (!data) {
>>  		ret = -ENOMEM;
>> -		goto error_free_buf_dir_name;
>> +		return ret;
>>  	}
>>  
>>  	ret = asprintf(&buffer_access, "/dev/iio:device%d", dev_num);
>>  	if (ret < 0) {
>>  		ret = -ENOMEM;
>> -		goto error_free_data;
>> +		return ret;
>>  	}
>>  
>>  	/* Attempt to open non blocking the access dev */
>> @@ -498,7 +554,7 @@ int main(int argc, char **argv)
>>  	if (fp == -1) { /* TODO: If it isn't there make the node */
>>  		ret = -errno;
>>  		fprintf(stderr, "Failed to open %s\n", buffer_access);
>> -		goto error_free_buffer_access;
>> +		return ret;
>>  	}
>>  
>>  	for (j = 0; j < num_loops; j++) {
>> @@ -510,8 +566,7 @@ int main(int argc, char **argv)
>>  
>>  			ret = poll(&pfd, 1, -1);
>>  			if (ret < 0) {
>> -				ret = -errno;
>> -				goto error_close_buffer_access;
>> +				return -errno;
>>  			} else if (ret == 0) {
>>  				continue;
>>  			}
>> @@ -536,46 +591,5 @@ int main(int argc, char **argv)
>>  				     num_channels);
>>  	}
>>  
>> -	/* Stop the buffer */
>> -	ret = write_sysfs_int("enable", buf_dir_name, 0);
>> -	if (ret < 0)
>> -		goto error_close_buffer_access;
>> -
>> -	if (!notrigger)
>> -		/* Disconnect the trigger - just write a dummy name. */
>> -		ret = write_sysfs_string("trigger/current_trigger",
>> -					 dev_dir_name, "NULL");
>> -		if (ret < 0)
>> -			fprintf(stderr, "Failed to write to %s\n",
>> -				dev_dir_name);
>> -
>> -error_close_buffer_access:
>> -	if (close(fp) == -1)
>> -		perror("Failed to close buffer");
>> -
>> -error_free_buffer_access:
>> -	free(buffer_access);
>> -error_free_data:
>> -	free(data);
>> -error_free_buf_dir_name:
>> -	free(buf_dir_name);
>> -error_free_channels:
>> -	for (i = num_channels - 1; i >= 0; i--) {
>> -		free(channels[i].name);
>> -		free(channels[i].generic_name);
>> -	}
>> -	free(channels);
>> -error_free_triggername:
>> -	if (datardytrigger)
>> -		free(trigger_name);
>> -error_disable_channels:
>> -	if (autochannels == AUTOCHANNELS_ACTIVE) {
>> -		ret = enable_disable_all_channels(dev_dir_name, 0);
>> -		if (ret)
>> -			fprintf(stderr, "Failed to disable all channels\n");
>> -	}
>> -error_free_dev_dir_name:
>> -	free(dev_dir_name);
>> -
>> -	return ret;
>> +	return 0;
>>  }
>>
> 

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