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.
Cc: John Kacur <[email protected]>
Cc: Steven Rostedt <[email protected]>
Fixes: b1696371d865 ("rtla: Helper functions for rtla")
Reported-by: Daniel Wagner <[email protected]>
Signed-off-by: Daniel Bristot de Oliveira <[email protected]>
---
tools/tracing/rtla/Makefile | 2 +-
tools/tracing/rtla/README.txt | 1 -
tools/tracing/rtla/src/utils.c | 83 +++++++++++++++++++++++++++-------
tools/tracing/rtla/src/utils.h | 1 +
4 files changed, 68 insertions(+), 19 deletions(-)
diff --git a/tools/tracing/rtla/Makefile b/tools/tracing/rtla/Makefile
index 11fb417abb42..90b8e20d1118 100644
--- a/tools/tracing/rtla/Makefile
+++ b/tools/tracing/rtla/Makefile
@@ -31,7 +31,7 @@ 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)
diff --git a/tools/tracing/rtla/README.txt b/tools/tracing/rtla/README.txt
index 6c88446f7e74..7bc0b931ddfd 100644
--- a/tools/tracing/rtla/README.txt
+++ b/tools/tracing/rtla/README.txt
@@ -13,7 +13,6 @@ following libraries:
- libtracefs
- libtraceevent
- - procps
It also depends on python3-docutils to compile man pages.
diff --git a/tools/tracing/rtla/src/utils.c b/tools/tracing/rtla/src/utils.c
index da2b590edaed..baf9003d5d41 100644
--- a/tools/tracing/rtla/src/utils.c
+++ b/tools/tracing/rtla/src/utils.c
@@ -3,7 +3,7 @@
* Copyright (C) 2021 Red Hat Inc, Daniel Bristot de Oliveira <[email protected]>
*/
-#include <proc/readproc.h>
+#include <dirent.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
@@ -262,6 +262,62 @@ int __set_sched_attr(int pid, struct sched_attr *attr)
return 0;
}
+
+/*
+ * procfs_is_workload_pid - check if a procfs entry contains a workload_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 *workload_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.
+ *
+ * Return: True if the proc_entry contains a comm file with workload_prefix*.
+ * Otherwise returns false.
+ */
+static int procfs_is_workload_pid(const char *workload_prefix, struct dirent *proc_entry)
+{
+ char comm_path[MAX_PATH], comm[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(comm_path, MAX_PATH, "/proc/%s/comm", proc_entry->d_name);
+ comm_fd = open(comm_path, O_RDONLY);
+ if (comm_fd < 0)
+ return 0;
+
+ memset(comm, 0, MAX_PATH);
+ retval = read(comm_fd, comm, MAX_PATH);
+
+ close(comm_fd);
+
+ if (retval <= 0)
+ return 0;
+
+ retval = !strncmp(workload_prefix, comm, strlen(workload_prefix));
+ if (!retval)
+ return 0;
+
+ /* comm already have \n */
+ debug_msg("Found workload pid:%s comm:%s", proc_entry->d_name, comm);
+
+ return 1;
+}
+
/*
* set_comm_sched_attr - set sched params to threads starting with char *comm
*
@@ -272,33 +328,26 @@ int __set_sched_attr(int pid, struct sched_attr *attr)
*/
int set_comm_sched_attr(const char *comm, 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;
- }
+ procfs = opendir("/proc");
- memset(&task, 0, sizeof(task));
+ while ((proc_entry = readdir(procfs))) {
- while (readproc(ptp, &task)) {
- retval = strncmp(comm, task.cmd, strlen(comm));
- if (retval)
+ retval = procfs_is_workload_pid(comm, proc_entry);
+ if (!retval)
continue;
- retval = __set_sched_attr(task.tid, attr);
+
+ /* procfs_is_workload_pid confirmed it is a pid */
+ retval = __set_sched_attr(atoi(proc_entry->d_name), attr);
if (retval)
goto out_err;
}
-
- closeproc(ptp);
return 0;
out_err:
- closeproc(ptp);
return 1;
}
diff --git a/tools/tracing/rtla/src/utils.h b/tools/tracing/rtla/src/utils.h
index fa08e374870a..4959a3e2c0d5 100644
--- a/tools/tracing/rtla/src/utils.h
+++ b/tools/tracing/rtla/src/utils.h
@@ -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); \
--
2.35.1
On Fri, 22 Apr 2022 12:01:31 +0200
Daniel Bristot de Oliveira <[email protected]> wrote:
> +
> +/*
> + * procfs_is_workload_pid - check if a procfs entry contains a workload_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 *workload_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.
> + *
> + * Return: True if the proc_entry contains a comm file with workload_prefix*.
> + * Otherwise returns false.
> + */
> +static int procfs_is_workload_pid(const char *workload_prefix, struct dirent *proc_entry)
> +{
> + char comm_path[MAX_PATH], comm[MAX_PATH];
This is probably fine (but there is one issue), but I would have done this
a little different.
int len = strlen(workload_prefix);
char comm[len + 1];
> + 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(comm_path, MAX_PATH, "/proc/%s/comm", proc_entry->d_name);
> + comm_fd = open(comm_path, O_RDONLY);
> + if (comm_fd < 0)
> + return 0;
> +
> + memset(comm, 0, MAX_PATH);
No need for the memset.
> + retval = read(comm_fd, comm, MAX_PATH);
retval = read(comm_fd, comm, len + 1);
> +
> + close(comm_fd);
> +
> + if (retval <= 0)
> + return 0;
if (comm[len] != '\n')
return 0;
> +
> + retval = !strncmp(workload_prefix, comm, strlen(workload_prefix));
What happens if strlen(workload_prefix) is greater than MAX_PATH? ;-)
retval = !strncmp(workload_prefix, comm, len);
But that's me. If you want to keep this as is, let me know.
-- Steve
> + if (!retval)
> + return 0;
> +
> + /* comm already have \n */
> + debug_msg("Found workload pid:%s comm:%s", proc_entry->d_name, comm);
> +
> + return 1;
> +}
> +
On 4/26/22 03:45, Steven Rostedt wrote:
> On Fri, 22 Apr 2022 12:01:31 +0200
> Daniel Bristot de Oliveira <[email protected]> wrote:
>
>
>> +
>> +/*
>> + * procfs_is_workload_pid - check if a procfs entry contains a workload_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 *workload_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.
>> + *
>> + * Return: True if the proc_entry contains a comm file with workload_prefix*.
>> + * Otherwise returns false.
>> + */
>> +static int procfs_is_workload_pid(const char *workload_prefix, struct dirent *proc_entry)
>> +{
>> + char comm_path[MAX_PATH], comm[MAX_PATH];
>
> This is probably fine (but there is one issue), but I would have done this
> a little different.
>
> int len = strlen(workload_prefix);
> char comm[len + 1];
>
>> + 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(comm_path, MAX_PATH, "/proc/%s/comm", proc_entry->d_name);
>> + comm_fd = open(comm_path, O_RDONLY);
>> + if (comm_fd < 0)
>> + return 0;
>> +
>> + memset(comm, 0, MAX_PATH);
>
> No need for the memset.
>
>> + retval = read(comm_fd, comm, MAX_PATH);
>
> retval = read(comm_fd, comm, len + 1);
>
>> +
>> + close(comm_fd);
>> +
>> + if (retval <= 0)
>> + return 0;
>
> if (comm[len] != '\n')
> return 0;
>
>> +
>> + retval = !strncmp(workload_prefix, comm, strlen(workload_prefix));
>
> What happens if strlen(workload_prefix) is greater than MAX_PATH? ;-)
That is a concern I had, but we have only two use cases on rtla so far, and they
are both bounded: 'timerlat/' 'osnoise/'...
I will add a check though.
>
> retval = !strncmp(workload_prefix, comm, len);
>
> But that's me. If you want to keep this as is, let me know.
I made these changes... but I am loosing the debug_msg() with the comm/pid that
matched. I am adding these messages (and I plan to add more) so I can use on
testing scripts...
At the same time, I can share a char buffer[MAX_PATH] for both the comm and
comm_path...
I think I will go this way (using a single buffer), adding a warning... and...
> -- Steve
>
>
>
>> + if (!retval)
>> + return 0;
also removing ! in the the revtal = !strcmp(...); if (!retval).
Thoughts?
-- Daniel
>> +
>> + /* comm already have \n */
>> + debug_msg("Found workload pid:%s comm:%s", proc_entry->d_name, comm);
>> +
>> + return 1;
>> +}
>> +