Commit dada03db authored by Daniel Bristot de Oliveira's avatar Daniel Bristot de Oliveira Committed by Steven Rostedt (Google)
Browse files

rtla: Remove procps-ng dependency 

Daniel Wagner reported to me that readproc.h got deprecated. Also,
while the procps-ng library was available on Fedora, it was not available
on RHEL, which is a piece of evidence that it was not that used.

rtla uses procps-ng only to find the PID of the tracers' workload.

I used the procps-ng library to avoid reinventing the wheel. But in this
case, reinventing the wheel took me less time than the time we already
took trying to work around problems.

Implement a function that reads /proc/ entries, checking if:
	- the entry is a directory
	- the directory name is composed only of digits (PID)
	- the directory contains the comm file
	- the comm file contains a comm that matches the tracers'
	  workload prefix.
	- then return true; otherwise, return false.

And use it instead of procps-ng.

Link: https://lkml.kernel.org/r/e8276e122ee9eb2c5a0ba8e673fb6488b924b825.1652423574.git.bristot@kernel.org



Cc: John Kacur <jkacur@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tao Zhou <tao.zhou@linux.dev>
Fixes: b1696371 ("rtla: Helper functions for rtla")
Reported-by: default avatarDaniel Wagner <dwagner@suse.de>
Reviewed-by: default avatarDaniel Wagner <dwagner@suse.de>
Signed-off-by: default avatarDaniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 941a53c3

tools/tracing/rtla/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -32,7 +32,7 @@ TRACEFS_HEADERS := $$($(PKG_CONFIG) --cflags libtracefs) 


CFLAGS	:=	-O -g -DVERSION=\"$(VERSION)\" $(FOPTS) $(MOPTS) $(WOPTS) $(TRACEFS_HEADERS)

LDFLAGS	:=	-ggdb

LIBS	:=	$$($(PKG_CONFIG) --libs libtracefs) -lprocps

LIBS	:=	$$($(PKG_CONFIG) --libs libtracefs)



SRC	:=	$(wildcard src/*.c)

HDR	:=	$(wildcard src/*.h)

tools/tracing/rtla/README.txt

+0 −1
Original line number Diff line number Diff line
@@ -11,7 +11,6 @@ RTLA depends on the following libraries and tools: 


 - libtracefs

 - libtraceevent

 - procps



It also depends on python3-docutils to compile man pages.

tools/tracing/rtla/src/utils.c

+85 −21
Original line number Diff line number Diff line
@@ -3,7 +3,7 @@ 
 * Copyright (C) 2021 Red Hat Inc, Daniel Bristot de Oliveira <bristot@kernel.org>

 */



#include <proc/readproc.h>

#include <dirent.h>

#include <stdarg.h>

#include <stdlib.h>

#include <string.h>
@@ -262,43 +262,107 @@ int __set_sched_attr(int pid, struct sched_attr *attr) 


	return 0;

}



/*

 * set_comm_sched_attr - set sched params to threads starting with char *comm

 * procfs_is_workload_pid - check if a procfs entry contains a comm_prefix* comm

 *

 * Check if the procfs entry is a directory of a process, and then check if the

 * process has a comm with the prefix set in char *comm_prefix. As the

 * current users of this function only check for kernel threads, there is no

 * need to check for the threads for the process.

 *

 * This function uses procps to list the currently running threads and then

 * set the sched_attr *attr to the threads that start with char *comm. It is

 * Return: True if the proc_entry contains a comm file with comm_prefix*.

 * Otherwise returns false.

 */

static int procfs_is_workload_pid(const char *comm_prefix, struct dirent *proc_entry)

{

	char buffer[MAX_PATH];

	int comm_fd, retval;

	char *t_name;



	if (proc_entry->d_type != DT_DIR)

		return 0;



	if (*proc_entry->d_name == '.')

		return 0;



	/* check if the string is a pid */

	for (t_name = proc_entry->d_name; t_name; t_name++) {

		if (!isdigit(*t_name))

			break;

	}



	if (*t_name != '\0')

		return 0;



	snprintf(buffer, MAX_PATH, "/proc/%s/comm", proc_entry->d_name);

	comm_fd = open(buffer, O_RDONLY);

	if (comm_fd < 0)

		return 0;



	memset(buffer, 0, MAX_PATH);

	retval = read(comm_fd, buffer, MAX_PATH);



	close(comm_fd);



	if (retval <= 0)

		return 0;



	retval = strncmp(comm_prefix, buffer, strlen(comm_prefix));

	if (retval)

		return 0;



	/* comm already have \n */

	debug_msg("Found workload pid:%s comm:%s", proc_entry->d_name, buffer);



	return 1;

}



/*

 * set_comm_sched_attr - set sched params to threads starting with char *comm_prefix

 *

 * This function uses procfs to list the currently running threads and then set the

 * sched_attr *attr to the threads that start with char *comm_prefix. It is

 * mainly used to set the priority to the kernel threads created by the

 * tracers.

 */

int set_comm_sched_attr(const char *comm, struct sched_attr *attr)

int set_comm_sched_attr(const char *comm_prefix, struct sched_attr *attr)

{

	int flags = PROC_FILLCOM | PROC_FILLSTAT;

	PROCTAB *ptp;

	proc_t task;

	struct dirent *proc_entry;

	DIR *procfs;

	int retval;



	ptp = openproc(flags);

	if (!ptp) {

		err_msg("error openproc()\n");

		return -ENOENT;

	if (strlen(comm_prefix) >= MAX_PATH) {

		err_msg("Command prefix is too long: %d < strlen(%s)\n",

			MAX_PATH, comm_prefix);

		return 1;

	}



	memset(&task, 0, sizeof(task));

	procfs = opendir("/proc");

	if (!procfs) {

		err_msg("Could not open procfs\n");

		return 1;

	}



	while (readproc(ptp, &task)) {

		retval = strncmp(comm, task.cmd, strlen(comm));

		if (retval)

	while ((proc_entry = readdir(procfs))) {



		retval = procfs_is_workload_pid(comm_prefix, proc_entry);

		if (!retval)

			continue;

		retval = __set_sched_attr(task.tid, attr);

		if (retval)



		/* procfs_is_workload_pid confirmed it is a pid */

		retval = __set_sched_attr(atoi(proc_entry->d_name), attr);

		if (retval) {

			err_msg("Error setting sched attributes for pid:%s\n", proc_entry->d_name);

			goto out_err;

		}



	closeproc(ptp);

		debug_msg("Set sched attributes for pid:%s\n", proc_entry->d_name);

	}

	return 0;



out_err:

	closeproc(ptp);

	closedir(procfs);

	return 1;

}

tools/tracing/rtla/src/utils.h

+2 −1
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
 * '18446744073709551615\0'

 */

#define BUFF_U64_STR_SIZE	24

#define MAX_PATH		1024



#define container_of(ptr, type, member)({			\

	const typeof(((type *)0)->member) *__mptr = (ptr);	\
@@ -53,5 +54,5 @@ struct sched_attr { 
};



int parse_prio(char *arg, struct sched_attr *sched_param);

int set_comm_sched_attr(const char *comm, struct sched_attr *attr);

int set_comm_sched_attr(const char *comm_prefix, struct sched_attr *attr);

int set_cpu_dma_latency(int32_t latency);