[PATCH 0/6] Refactor the APIs for tracing options

[PATCH 0/6] Refactor the APIs for tracing options

[Yordan Karadzhov (VMware)]

Yordan Karadzhov (VMware) (6):
  libtracefs: Fix issues with tracefs_option_id()
  libtracefs: Modify the arguments of tracefs_option_is_set()
  libtracefs: Encapsulate "struct tracefs_options_mask"
  libtracefs: Move the "options" code to  tracefs-instance.c
  libtracefs: Option's bit masks to be owned by the instance
  libtracefs: Rename tracefs_option_is_set()

 Documentation/libtracefs-option-get.txt |   4 +-
 include/tracefs.h                       |  15 +-
 src/tracefs-instance.c                  | 266 +++++++++++++++++++++++
 src/tracefs-tools.c                     | 276 ------------------------
 4 files changed, 273 insertions(+), 288 deletions(-)

-- 
2.27.0

[PATCH 1/6] libtracefs: Fix issues with tracefs_option_id()

[Yordan Karadzhov (VMware)]

Few mistakes have been made when introducing this API function.
First of all, its declaration is missing from the header file.
In addition to this the argument type is missing "const".

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 include/tracefs.h   | 1 +
 src/tracefs-tools.c | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/tracefs.h b/include/tracefs.h
index 05bd0ef..fbd7db5 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -145,5 +145,6 @@ bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_o
 int tracefs_option_enable(struct tracefs_instance *instance, enum tracefs_option_id id);
 int tracefs_option_diasble(struct tracefs_instance *instance, enum tracefs_option_id id);
 const char *tracefs_option_name(enum tracefs_option_id id);
+enum tracefs_option_id tracefs_option_id(const char *name);
 
 #endif /* _TRACE_FS_H */
diff --git a/src/tracefs-tools.c b/src/tracefs-tools.c
index e2dfc7b..51a7971 100644
--- a/src/tracefs-tools.c
+++ b/src/tracefs-tools.c
@@ -181,7 +181,7 @@ const char *tracefs_option_name(enum tracefs_option_id id)
  * Returns trace option ID or TRACEFS_OPTION_INVALID in case of an error or
  * unknown option name.
  */
-enum tracefs_option_id tracefs_option_id(char *name)
+enum tracefs_option_id tracefs_option_id(const char *name)
 {
 	int i;
 
-- 
2.27.0

[PATCH 2/6] libtracefs: Modify the arguments of tracefs_option_is_set()

[Yordan Karadzhov (VMware)]

This function is supposed to take as argument a mask returned by
"tracefs_options_get_supported()" or "tracefs_options_get_enabled()",
hence this argument must be a pointer.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 include/tracefs.h   | 4 ++--
 src/tracefs-tools.c | 5 +++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/tracefs.h b/include/tracefs.h
index fbd7db5..5c4e50d 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -136,8 +136,8 @@ struct tracefs_options_mask {
 };
 void tracefs_option_set(struct tracefs_options_mask *options, enum tracefs_option_id id);
 void tracefs_option_clear(struct tracefs_options_mask *options, enum tracefs_option_id id);
-bool tracefs_option_is_set(struct tracefs_options_mask options, enum tracefs_option_id id);
-
+bool tracefs_option_is_set(struct tracefs_options_mask *options,
+			   enum tracefs_option_id id);
 struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
 bool tracefs_option_is_supported(struct tracefs_instance *instance, enum tracefs_option_id id);
 struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
diff --git a/src/tracefs-tools.c b/src/tracefs-tools.c
index 51a7971..3b5f773 100644
--- a/src/tracefs-tools.c
+++ b/src/tracefs-tools.c
@@ -359,10 +359,11 @@ bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_o
  * Returns true if an option with given id is set in the bitmask,
  * false if it is not set.
  */
-bool tracefs_option_is_set(struct tracefs_options_mask options, enum tracefs_option_id id)
+bool tracefs_option_is_set(struct tracefs_options_mask *options,
+			   enum tracefs_option_id id)
 {
 	if (id > TRACEFS_OPTION_INVALID)
-		return options.mask & (1ULL << (id - 1));
+		return options->mask & (1ULL << (id - 1));
 	return false;
 }
 
-- 
2.27.0

[PATCH 3/6] libtracefs: Encapsulate "struct tracefs_options_mask"

[Yordan Karadzhov (VMware)]

The definition of the mask gets hidden from the user. This way we will
be able to modify this definition in the future, without breaking the
API. Such a modification will be compulsory, if too many new tracing
options are added in the future. Note that encapsulating the mask
definition, requires two API methods to be eliminated, however those
methods have no particular use-cases for the moment.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 include/tracefs.h   |  6 +-----
 src/tracefs-tools.c | 33 +++++++++++----------------------
 2 files changed, 12 insertions(+), 27 deletions(-)

diff --git a/include/tracefs.h b/include/tracefs.h
index 5c4e50d..0665e8d 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -131,11 +131,7 @@ enum tracefs_option_id {
 };
 #define TRACEFS_OPTION_MAX (TRACEFS_OPTION_VERBOSE + 1)
 
-struct tracefs_options_mask {
-	unsigned long long	mask;
-};
-void tracefs_option_set(struct tracefs_options_mask *options, enum tracefs_option_id id);
-void tracefs_option_clear(struct tracefs_options_mask *options, enum tracefs_option_id id);
+struct tracefs_options_mask;
 bool tracefs_option_is_set(struct tracefs_options_mask *options,
 			   enum tracefs_option_id id);
 struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
diff --git a/src/tracefs-tools.c b/src/tracefs-tools.c
index 3b5f773..11a4c8c 100644
--- a/src/tracefs-tools.c
+++ b/src/tracefs-tools.c
@@ -19,6 +19,10 @@
 
 #define TRACE_CTRL	"tracing_on"
 
+struct tracefs_options_mask {
+	unsigned long long	mask;
+};
+
 static const char * const options_map[] = {
 	"unknown",
 	"annotate",
@@ -197,6 +201,13 @@ enum tracefs_option_id tracefs_option_id(const char *name)
 	return TRACEFS_OPTION_INVALID;
 }
 
+static void tracefs_option_set(struct tracefs_options_mask *options,
+			       enum tracefs_option_id id)
+{
+	if (options && id > TRACEFS_OPTION_INVALID)
+		options->mask |= (1ULL << (id - 1));
+}
+
 static struct tracefs_options_mask *trace_get_options(struct tracefs_instance *instance,
 						      bool enabled)
 {
@@ -366,25 +377,3 @@ bool tracefs_option_is_set(struct tracefs_options_mask *options,
 		return options->mask & (1ULL << (id - 1));
 	return false;
 }
-
-/**
- * tracefs_option_set - Set option in options bitmask
- * @options: Pointer to a bitmask with options
- * @id: trace option id
- */
-void tracefs_option_set(struct tracefs_options_mask *options, enum tracefs_option_id id)
-{
-	if (options && id > TRACEFS_OPTION_INVALID)
-		options->mask |= (1ULL << (id - 1));
-}
-
-/**
- * tracefs_option_clear - Clear option from options bitmask
- * @options: Pointer to a bitmask with options
- * @id: trace option id
- */
-void tracefs_option_clear(struct tracefs_options_mask *options, enum tracefs_option_id id)
-{
-	if (options && id > TRACEFS_OPTION_INVALID)
-		options->mask &= ~(1ULL << (id - 1));
-}
-- 
2.27.0

Re: [PATCH 3/6] libtracefs: Encapsulate "struct tracefs_options_mask"

[Steven Rostedt]

On Fri,  2 Apr 2021 16:19:44 +0300
"Yordan Karadzhov (VMware)" <y.karadz@gmail.com> wrote:

> @@ -197,6 +201,13 @@ enum tracefs_option_id tracefs_option_id(const char *name)
>  	return TRACEFS_OPTION_INVALID;
>  }
>  
> +static void tracefs_option_set(struct tracefs_options_mask *options,
> +			       enum tracefs_option_id id)

Patch is fine, but lets rename this function to:

	trace_option_set()

As functions named "tracefs_*()" should be used only by functions that are
for the API or will be for the API (staging functions).

-- Steve


> +{
> +	if (options && id > TRACEFS_OPTION_INVALID)
> +		options->mask |= (1ULL << (id - 1));
> +}
> +
>  static struct tracefs_options_mask *trace_get_options(struct tracefs_instance *instance,
>  						      bool enabled)
>  {

[PATCH 4/6] libtracefs: Move the "options" code to tracefs-instance.c

[Yordan Karadzhov (VMware)]

We would like the instance object to own two bit masks (struct
tracefs_options_mask) associated with all supported and all enabled
options. However, the definition of the instance itself is not public,
hence the code implementing the "options" related APIs has to in the
same source file as the definition of the instance.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 src/tracefs-instance.c | 266 +++++++++++++++++++++++++++++++++++++++++
 src/tracefs-tools.c    | 266 -----------------------------------------
 2 files changed, 266 insertions(+), 266 deletions(-)

diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
index 0df313c..49645eb 100644
--- a/src/tracefs-instance.c
+++ b/src/tracefs-instance.c
@@ -18,6 +18,10 @@
 #include "tracefs.h"
 #include "tracefs-local.h"
 
+struct tracefs_options_mask {
+	unsigned long long	mask;
+};
+
 #define FLAG_INSTANCE_NEWLY_CREATED	(1 << 0)
 struct tracefs_instance {
 	char	*trace_dir;
@@ -587,3 +591,265 @@ out:
 	free(all_clocks);
 	return ret;
 }
+
+static const char * const options_map[] = {
+	"unknown",
+	"annotate",
+	"bin",
+	"blk_cgname",
+	"blk_cgroup",
+	"blk_classic",
+	"block",
+	"context-info",
+	"disable_on_free",
+	"display-graph",
+	"event-fork",
+	"funcgraph-abstime",
+	"funcgraph-cpu",
+	"funcgraph-duration",
+	"funcgraph-irqs",
+	"funcgraph-overhead",
+	"funcgraph-overrun",
+	"funcgraph-proc",
+	"funcgraph-tail",
+	"func_stack_trace",
+	"function-fork",
+	"function-trace",
+	"graph-time",
+	"hex",
+	"irq-info",
+	"latency-format",
+	"markers",
+	"overwrite",
+	"pause-on-trace",
+	"printk-msg-only",
+	"print-parent",
+	"raw",
+	"record-cmd",
+	"record-tgid",
+	"sleep-time",
+	"stacktrace",
+	"sym-addr",
+	"sym-offset",
+	"sym-userobj",
+	"trace_printk",
+	"userstacktrace",
+	"verbose" };
+
+/**
+ * tracefs_option_name - Get trace option name from id
+ * @id: trace option id
+ *
+ * Returns string with option name, or "unknown" in case of not known option id.
+ * The returned string must *not* be freed.
+ */
+const char *tracefs_option_name(enum tracefs_option_id id)
+{
+	/* Make sure options map contains all the options */
+	BUILD_BUG_ON(ARRAY_SIZE(options_map) != TRACEFS_OPTION_MAX);
+
+	if (id < TRACEFS_OPTION_MAX)
+		return options_map[id];
+
+	return options_map[0];
+}
+
+/**
+ * tracefs_option_id - Get trace option ID from name
+ * @name: trace option name
+ *
+ * Returns trace option ID or TRACEFS_OPTION_INVALID in case of an error or
+ * unknown option name.
+ */
+enum tracefs_option_id tracefs_option_id(const char *name)
+{
+	int i;
+
+	if (!name)
+		return TRACEFS_OPTION_INVALID;
+
+	for (i = 0; i < TRACEFS_OPTION_MAX; i++) {
+		if (strlen(name) == strlen(options_map[i]) &&
+		    !strcmp(options_map[i], name))
+			return i;
+	}
+
+	return TRACEFS_OPTION_INVALID;
+}
+
+static void tracefs_option_set(struct tracefs_options_mask *options,
+			       enum tracefs_option_id id)
+{
+	if (options && id > TRACEFS_OPTION_INVALID)
+		options->mask |= (1ULL << (id - 1));
+}
+
+static struct tracefs_options_mask *trace_get_options(struct tracefs_instance *instance,
+						      bool enabled)
+{
+	struct tracefs_options_mask *bitmask;
+	enum tracefs_option_id id;
+	char file[PATH_MAX];
+	struct dirent *dent;
+	char *dname = NULL;
+	DIR *dir = NULL;
+	long long val;
+
+	bitmask = calloc(1, sizeof(struct tracefs_options_mask));
+	if (!bitmask)
+		return NULL;
+	dname = tracefs_instance_get_file(instance, "options");
+	if (!dname)
+		goto error;
+	dir = opendir(dname);
+	if (!dir)
+		goto error;
+
+	while ((dent = readdir(dir))) {
+		if (*dent->d_name == '.')
+			continue;
+		if (enabled) {
+			snprintf(file, PATH_MAX, "options/%s", dent->d_name);
+			if (tracefs_instance_file_read_number(instance, file, &val) != 0 ||
+			    val != 1)
+				continue;
+		}
+		id = tracefs_option_id(dent->d_name);
+		if (id != TRACEFS_OPTION_INVALID)
+			tracefs_option_set(bitmask, id);
+	}
+	closedir(dir);
+	tracefs_put_tracing_file(dname);
+
+	return bitmask;
+
+error:
+	if (dir)
+		closedir(dir);
+	tracefs_put_tracing_file(dname);
+	free(bitmask);
+	return NULL;
+}
+
+/**
+ * tracefs_options_get_supported - Get all supported trace options in given instance
+ * @instance: ftrace instance, can be NULL for the top instance
+ *
+ * Returns allocated bitmask structure with all trace options, supported in given
+ * instance, or NULL in case of an error. The returned structure must be freed with free()
+ */
+struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance)
+{
+	return trace_get_options(instance, false);
+}
+
+/**
+ * tracefs_options_get_enabled - Get all currently enabled trace options in given instance
+ * @instance: ftrace instance, can be NULL for the top instance
+ *
+ * Returns allocated bitmask structure with all trace options, enabled in given
+ * instance, or NULL in case of an error. The returned structure must be freed with free()
+ */
+struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance)
+{
+	return trace_get_options(instance, true);
+}
+
+static int trace_config_option(struct tracefs_instance *instance,
+			       enum tracefs_option_id id, bool set)
+{
+	char *set_str = set ? "1" : "0";
+	char file[PATH_MAX];
+	const char *name;
+
+	name = tracefs_option_name(id);
+	if (!name)
+		return -1;
+
+	snprintf(file, PATH_MAX, "options/%s", name);
+	if (strlen(set_str) != tracefs_instance_file_write(instance, file, set_str))
+		return -1;
+	return 0;
+}
+
+/**
+ * tracefs_option_enable - Enable trace option
+ * @instance: ftrace instance, can be NULL for the top instance
+ * @id: trace option id
+ *
+ * Returns -1 in case of an error or 0 otherwise
+ */
+int tracefs_option_enable(struct tracefs_instance *instance, enum tracefs_option_id id)
+{
+	return trace_config_option(instance, id, true);
+}
+
+/**
+ * tracefs_option_diasble - Disable trace option
+ * @instance: ftrace instance, can be NULL for the top instance
+ * @id: trace option id
+ *
+ * Returns -1 in case of an error or 0 otherwise
+ */
+int tracefs_option_diasble(struct tracefs_instance *instance, enum tracefs_option_id id)
+{
+	return trace_config_option(instance, id, false);
+}
+
+/**
+ * tracefs_option_is_supported - Check if an option is supported
+ * @instance: ftrace instance, can be NULL for the top instance
+ * @id: trace option id
+ *
+ * Returns true if an option with given id is supported by the system, false if
+ * it is not supported.
+ */
+bool tracefs_option_is_supported(struct tracefs_instance *instance, enum tracefs_option_id id)
+{
+	const char *name = tracefs_option_name(id);
+	char file[PATH_MAX];
+
+	if (!name)
+		return false;
+	snprintf(file, PATH_MAX, "options/%s", name);
+	return tracefs_file_exists(instance, file);
+}
+
+/**
+ * tracefs_option_is_enabled - Check if an option is enabled in given instance
+ * @instance: ftrace instance, can be NULL for the top instance
+ * @id: trace option id
+ *
+ * Returns true if an option with given id is enabled in the given instance,
+ * false if it is not enabled.
+ */
+bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_option_id id)
+{
+	const char *name = tracefs_option_name(id);
+	char file[PATH_MAX];
+	long long res;
+
+	if (!name)
+		return false;
+	snprintf(file, PATH_MAX, "options/%s", name);
+	if (!tracefs_instance_file_read_number(instance, file, &res) && res)
+		return true;
+
+	return false;
+}
+
+/**
+ * tracefs_option_is_set - Check if given option is set in the bitmask
+ * @options: Options bitmask
+ * @id: trace option id
+ *
+ * Returns true if an option with given id is set in the bitmask,
+ * false if it is not set.
+ */
+bool tracefs_option_is_set(struct tracefs_options_mask *options,
+			   enum tracefs_option_id id)
+{
+	if (id > TRACEFS_OPTION_INVALID)
+		return options->mask & (1ULL << (id - 1));
+	return false;
+}
diff --git a/src/tracefs-tools.c b/src/tracefs-tools.c
index 11a4c8c..8f763a4 100644
--- a/src/tracefs-tools.c
+++ b/src/tracefs-tools.c
@@ -19,54 +19,6 @@
 
 #define TRACE_CTRL	"tracing_on"
 
-struct tracefs_options_mask {
-	unsigned long long	mask;
-};
-
-static const char * const options_map[] = {
-	"unknown",
-	"annotate",
-	"bin",
-	"blk_cgname",
-	"blk_cgroup",
-	"blk_classic",
-	"block",
-	"context-info",
-	"disable_on_free",
-	"display-graph",
-	"event-fork",
-	"funcgraph-abstime",
-	"funcgraph-cpu",
-	"funcgraph-duration",
-	"funcgraph-irqs",
-	"funcgraph-overhead",
-	"funcgraph-overrun",
-	"funcgraph-proc",
-	"funcgraph-tail",
-	"func_stack_trace",
-	"function-fork",
-	"function-trace",
-	"graph-time",
-	"hex",
-	"irq-info",
-	"latency-format",
-	"markers",
-	"overwrite",
-	"pause-on-trace",
-	"printk-msg-only",
-	"print-parent",
-	"raw",
-	"record-cmd",
-	"record-tgid",
-	"sleep-time",
-	"stacktrace",
-	"sym-addr",
-	"sym-offset",
-	"sym-userobj",
-	"trace_printk",
-	"userstacktrace",
-	"verbose" };
-
 static int trace_on_off(int fd, bool on)
 {
 	const char *val = on ? "1" : "0";
@@ -159,221 +111,3 @@ int tracefs_trace_off_fd(int fd)
 		return -1;
 	return trace_on_off(fd, false);
 }
-
-/**
- * tracefs_option_name - Get trace option name from id
- * @id: trace option id
- *
- * Returns string with option name, or "unknown" in case of not known option id.
- * The returned string must *not* be freed.
- */
-const char *tracefs_option_name(enum tracefs_option_id id)
-{
-	/* Make sure options map contains all the options */
-	BUILD_BUG_ON(ARRAY_SIZE(options_map) != TRACEFS_OPTION_MAX);
-
-	if (id < TRACEFS_OPTION_MAX)
-		return options_map[id];
-
-	return options_map[0];
-}
-
-/**
- * tracefs_option_id - Get trace option ID from name
- * @name: trace option name
- *
- * Returns trace option ID or TRACEFS_OPTION_INVALID in case of an error or
- * unknown option name.
- */
-enum tracefs_option_id tracefs_option_id(const char *name)
-{
-	int i;
-
-	if (!name)
-		return TRACEFS_OPTION_INVALID;
-
-	for (i = 0; i < TRACEFS_OPTION_MAX; i++) {
-		if (strlen(name) == strlen(options_map[i]) &&
-		    !strcmp(options_map[i], name))
-			return i;
-	}
-
-	return TRACEFS_OPTION_INVALID;
-}
-
-static void tracefs_option_set(struct tracefs_options_mask *options,
-			       enum tracefs_option_id id)
-{
-	if (options && id > TRACEFS_OPTION_INVALID)
-		options->mask |= (1ULL << (id - 1));
-}
-
-static struct tracefs_options_mask *trace_get_options(struct tracefs_instance *instance,
-						      bool enabled)
-{
-	struct tracefs_options_mask *bitmask;
-	enum tracefs_option_id id;
-	char file[PATH_MAX];
-	struct dirent *dent;
-	char *dname = NULL;
-	DIR *dir = NULL;
-	long long val;
-
-	bitmask = calloc(1, sizeof(struct tracefs_options_mask));
-	if (!bitmask)
-		return NULL;
-	dname = tracefs_instance_get_file(instance, "options");
-	if (!dname)
-		goto error;
-	dir = opendir(dname);
-	if (!dir)
-		goto error;
-
-	while ((dent = readdir(dir))) {
-		if (*dent->d_name == '.')
-			continue;
-		if (enabled) {
-			snprintf(file, PATH_MAX, "options/%s", dent->d_name);
-			if (tracefs_instance_file_read_number(instance, file, &val) != 0 ||
-			    val != 1)
-				continue;
-		}
-		id = tracefs_option_id(dent->d_name);
-		if (id != TRACEFS_OPTION_INVALID)
-			tracefs_option_set(bitmask, id);
-	}
-	closedir(dir);
-	tracefs_put_tracing_file(dname);
-
-	return bitmask;
-
-error:
-	if (dir)
-		closedir(dir);
-	tracefs_put_tracing_file(dname);
-	free(bitmask);
-	return NULL;
-}
-
-/**
- * tracefs_options_get_supported - Get all supported trace options in given instance
- * @instance: ftrace instance, can be NULL for the top instance
- *
- * Returns allocated bitmask structure with all trace options, supported in given
- * instance, or NULL in case of an error. The returned structure must be freed with free()
- */
-struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance)
-{
-	return trace_get_options(instance, false);
-}
-
-/**
- * tracefs_options_get_enabled - Get all currently enabled trace options in given instance
- * @instance: ftrace instance, can be NULL for the top instance
- *
- * Returns allocated bitmask structure with all trace options, enabled in given
- * instance, or NULL in case of an error. The returned structure must be freed with free()
- */
-struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance)
-{
-	return trace_get_options(instance, true);
-}
-
-static int trace_config_option(struct tracefs_instance *instance,
-			       enum tracefs_option_id id, bool set)
-{
-	char *set_str = set ? "1" : "0";
-	char file[PATH_MAX];
-	const char *name;
-
-	name = tracefs_option_name(id);
-	if (!name)
-		return -1;
-
-	snprintf(file, PATH_MAX, "options/%s", name);
-	if (strlen(set_str) != tracefs_instance_file_write(instance, file, set_str))
-		return -1;
-	return 0;
-}
-
-/**
- * tracefs_option_enable - Enable trace option
- * @instance: ftrace instance, can be NULL for the top instance
- * @id: trace option id
- *
- * Returns -1 in case of an error or 0 otherwise
- */
-int tracefs_option_enable(struct tracefs_instance *instance, enum tracefs_option_id id)
-{
-	return trace_config_option(instance, id, true);
-}
-
-/**
- * tracefs_option_diasble - Disable trace option
- * @instance: ftrace instance, can be NULL for the top instance
- * @id: trace option id
- *
- * Returns -1 in case of an error or 0 otherwise
- */
-int tracefs_option_diasble(struct tracefs_instance *instance, enum tracefs_option_id id)
-{
-	return trace_config_option(instance, id, false);
-}
-
-/**
- * tracefs_option_is_supported - Check if an option is supported
- * @instance: ftrace instance, can be NULL for the top instance
- * @id: trace option id
- *
- * Returns true if an option with given id is supported by the system, false if
- * it is not supported.
- */
-bool tracefs_option_is_supported(struct tracefs_instance *instance, enum tracefs_option_id id)
-{
-	const char *name = tracefs_option_name(id);
-	char file[PATH_MAX];
-
-	if (!name)
-		return false;
-	snprintf(file, PATH_MAX, "options/%s", name);
-	return tracefs_file_exists(instance, file);
-}
-
-/**
- * tracefs_option_is_enabled - Check if an option is enabled in given instance
- * @instance: ftrace instance, can be NULL for the top instance
- * @id: trace option id
- *
- * Returns true if an option with given id is enabled in the given instance,
- * false if it is not enabled.
- */
-bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_option_id id)
-{
-	const char *name = tracefs_option_name(id);
-	char file[PATH_MAX];
-	long long res;
-
-	if (!name)
-		return false;
-	snprintf(file, PATH_MAX, "options/%s", name);
-	if (!tracefs_instance_file_read_number(instance, file, &res) && res)
-		return true;
-
-	return false;
-}
-
-/**
- * tracefs_option_is_set - Check if given option is set in the bitmask
- * @options: Options bitmask
- * @id: trace option id
- *
- * Returns true if an option with given id is set in the bitmask,
- * false if it is not set.
- */
-bool tracefs_option_is_set(struct tracefs_options_mask *options,
-			   enum tracefs_option_id id)
-{
-	if (id > TRACEFS_OPTION_INVALID)
-		return options->mask & (1ULL << (id - 1));
-	return false;
-}
-- 
2.27.0

Re: [PATCH 4/6] libtracefs: Move the "options" code to tracefs-instance.c

[Steven Rostedt]

On Fri,  2 Apr 2021 16:19:45 +0300
"Yordan Karadzhov (VMware)" <y.karadz@gmail.com> wrote:

> We would like the instance object to own two bit masks (struct
> tracefs_options_mask) associated with all supported and all enabled
> options. However, the definition of the instance itself is not public,
> hence the code implementing the "options" related APIs has to in the
> same source file as the definition of the instance.

The above is not true. We can keep the code in tracefs-tools.c and make it
"public" for the internal use of the library, but not part of the API. To
do so, you place shared structures and functions in include/tracefs-local.h,
and mark all non static functions with "__hidden" which will keep it from
being used outside the library.

Do you still feel that the moving of this code is needed?

-- Steve


> 
> Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
> ---
>  src/tracefs-instance.c | 266 +++++++++++++++++++++++++++++++++++++++++
>  src/tracefs-tools.c    | 266 -----------------------------------------
>  2 files changed, 266 insertions(+), 266 deletions(-)

Re: [PATCH 4/6] libtracefs: Move the "options" code to tracefs-instance.c

[Steven Rostedt]

On Fri, 2 Apr 2021 10:17:56 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> Do you still feel that the moving of this code is needed?


The rest of the patch series looks fine. Can you send a v2? I'll let you
and Tzvetomir decide if you want the code from this patch moved to the
instance file. But at a minimum, lets rename tracefs_option_set() to
trace_option_set().

Thanks!

-- Steve

Re: [PATCH 4/6] libtracefs: Move the "options" code to tracefs-instance.c

[Yordan Karadzhov]

On 2.04.21 г. 17:17, Steven Rostedt wrote:
> On Fri,  2 Apr 2021 16:19:45 +0300
> "Yordan Karadzhov (VMware)" <y.karadz@gmail.com> wrote:
>
>> We would like the instance object to own two bit masks (struct
>> tracefs_options_mask) associated with all supported and all enabled
>> options. However, the definition of the instance itself is not public,
>> hence the code implementing the "options" related APIs has to in the
>> same source file as the definition of the instance.
> The above is not true. We can keep the code in tracefs-tools.c and make it
> "public" for the internal use of the library, but not part of the API. To
> do so, you place shared structures and functions in include/tracefs-local.h,
> and mark all non static functions with "__hidden" which will keep it from
> being used outside the library.
>
> Do you still feel that the moving of this code is needed?

Hi Steven,

Thanks a lot for the review!

I wasn't sure if it is OK to move the "tracefs_instance" struct to 
"include/tracefs-local.h". If this is the case, then I will drop this 
patch and send v2.

cheers,

Yordan






>
> -- Steve
>
>
>> Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
>> ---
>>   src/tracefs-instance.c | 266 +++++++++++++++++++++++++++++++++++++++++
>>   src/tracefs-tools.c    | 266 -----------------------------------------
>>   2 files changed, 266 insertions(+), 266 deletions(-)

[PATCH 5/6] libtracefs: Option's bit masks to be owned by the instance

[Yordan Karadzhov (VMware)]

If the instance owns two mask objects, we no longer need to
dynamically allocate memory in tracefs_options_get_supported() and
tracefs_options_get_enabled(). This will simplify the code on the
caller side, since the user is no longer responsible for freeing
those masks.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 Documentation/libtracefs-option-get.txt |  4 +---
 include/tracefs.h                       |  6 +++---
 src/tracefs-instance.c                  | 24 ++++++++++++------------
 3 files changed, 16 insertions(+), 18 deletions(-)

diff --git a/Documentation/libtracefs-option-get.txt b/Documentation/libtracefs-option-get.txt
index 9b3cb56..3290f24 100644
--- a/Documentation/libtracefs-option-get.txt
+++ b/Documentation/libtracefs-option-get.txt
@@ -52,14 +52,13 @@ EXAMPLE
 --
 #include <tracefs.h>
 ...
-struct tracefs_options_mask *options;
+const struct tracefs_options_mask *options;
 ...
 options = tracefs_options_get_supported(NULL);
 if (!options) {
 	/* Failed to get supported options */
 } else {
 	...
-	free(options);
 }
 ...
 options = tracefs_options_get_enabled(NULL);
@@ -67,7 +66,6 @@ if (!options) {
 	/* Failed to get options, enabled in the top instance */
 } else {
 	...
-	free(options);
 }
 ...
 
diff --git a/include/tracefs.h b/include/tracefs.h
index 0665e8d..9efa91a 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -132,11 +132,11 @@ enum tracefs_option_id {
 #define TRACEFS_OPTION_MAX (TRACEFS_OPTION_VERBOSE + 1)
 
 struct tracefs_options_mask;
-bool tracefs_option_is_set(struct tracefs_options_mask *options,
+bool tracefs_option_is_set(const struct tracefs_options_mask *options,
 			   enum tracefs_option_id id);
-struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
+const struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
 bool tracefs_option_is_supported(struct tracefs_instance *instance, enum tracefs_option_id id);
-struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
+const struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
 bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_option_id id);
 int tracefs_option_enable(struct tracefs_instance *instance, enum tracefs_option_id id);
 int tracefs_option_diasble(struct tracefs_instance *instance, enum tracefs_option_id id);
diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
index 49645eb..9cb4b6d 100644
--- a/src/tracefs-instance.c
+++ b/src/tracefs-instance.c
@@ -27,6 +27,8 @@ struct tracefs_instance {
 	char	*trace_dir;
 	char	*name;
 	int	flags;
+	struct tracefs_options_mask	supported_opts;
+	struct tracefs_options_mask	enabled_opts;
 };
 
 /**
@@ -695,9 +697,8 @@ static struct tracefs_options_mask *trace_get_options(struct tracefs_instance *i
 	DIR *dir = NULL;
 	long long val;
 
-	bitmask = calloc(1, sizeof(struct tracefs_options_mask));
-	if (!bitmask)
-		return NULL;
+	bitmask = enabled? &instance->enabled_opts : &instance->supported_opts;
+
 	dname = tracefs_instance_get_file(instance, "options");
 	if (!dname)
 		goto error;
@@ -727,7 +728,6 @@ error:
 	if (dir)
 		closedir(dir);
 	tracefs_put_tracing_file(dname);
-	free(bitmask);
 	return NULL;
 }
 
@@ -735,10 +735,10 @@ error:
  * tracefs_options_get_supported - Get all supported trace options in given instance
  * @instance: ftrace instance, can be NULL for the top instance
  *
- * Returns allocated bitmask structure with all trace options, supported in given
- * instance, or NULL in case of an error. The returned structure must be freed with free()
+ * Returns bitmask structure with all trace options, supported in given instance,
+ * or NULL in case of an error.
  */
-struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance)
+const struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance)
 {
 	return trace_get_options(instance, false);
 }
@@ -747,10 +747,10 @@ struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instan
  * tracefs_options_get_enabled - Get all currently enabled trace options in given instance
  * @instance: ftrace instance, can be NULL for the top instance
  *
- * Returns allocated bitmask structure with all trace options, enabled in given
- * instance, or NULL in case of an error. The returned structure must be freed with free()
+ * Returns allocated bitmask structure with all trace options, enabled in given instance,
+ * or NULL in case of an error.
  */
-struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance)
+const struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance)
 {
 	return trace_get_options(instance, true);
 }
@@ -758,7 +758,7 @@ struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance
 static int trace_config_option(struct tracefs_instance *instance,
 			       enum tracefs_option_id id, bool set)
 {
-	char *set_str = set ? "1" : "0";
+	const char *set_str = set ? "1" : "0";
 	char file[PATH_MAX];
 	const char *name;
 
@@ -846,7 +846,7 @@ bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_o
  * Returns true if an option with given id is set in the bitmask,
  * false if it is not set.
  */
-bool tracefs_option_is_set(struct tracefs_options_mask *options,
+bool tracefs_option_is_set(const struct tracefs_options_mask *options,
 			   enum tracefs_option_id id)
 {
 	if (id > TRACEFS_OPTION_INVALID)
-- 
2.27.0

Re: [PATCH 5/6] libtracefs: Option's bit masks to be owned by the instance

[Tzvetomir Stoyanov]

On Fri, Apr 2, 2021 at 4:20 PM Yordan Karadzhov (VMware)
<y.karadz@gmail.com> wrote:
>
> If the instance owns two mask objects, we no longer need to
> dynamically allocate memory in tracefs_options_get_supported() and
> tracefs_options_get_enabled(). This will simplify the code on the
> caller side, since the user is no longer responsible for freeing
> those masks.
>
> Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
> ---
>  Documentation/libtracefs-option-get.txt |  4 +---
>  include/tracefs.h                       |  6 +++---
>  src/tracefs-instance.c                  | 24 ++++++++++++------------
>  3 files changed, 16 insertions(+), 18 deletions(-)
>
> diff --git a/Documentation/libtracefs-option-get.txt b/Documentation/libtracefs-option-get.txt
> index 9b3cb56..3290f24 100644
> --- a/Documentation/libtracefs-option-get.txt
> +++ b/Documentation/libtracefs-option-get.txt
> @@ -52,14 +52,13 @@ EXAMPLE
>  --
>  #include <tracefs.h>
>  ...
> -struct tracefs_options_mask *options;
> +const struct tracefs_options_mask *options;
>  ...
>  options = tracefs_options_get_supported(NULL);
>  if (!options) {
>         /* Failed to get supported options */
>  } else {
>         ...
> -       free(options);
>  }
>  ..

The description of the return value of tracefs_options_get_supported()
and tracefs_options_get_enabled() should be changed also, as it
suggests to free the return value;

>  options = tracefs_options_get_enabled(NULL);
> @@ -67,7 +66,6 @@ if (!options) {
>         /* Failed to get options, enabled in the top instance */
>  } else {
>         ...
> -       free(options);
>  }
>  ...
>
> diff --git a/include/tracefs.h b/include/tracefs.h
> index 0665e8d..9efa91a 100644
> --- a/include/tracefs.h
> +++ b/include/tracefs.h
> @@ -132,11 +132,11 @@ enum tracefs_option_id {
>  #define TRACEFS_OPTION_MAX (TRACEFS_OPTION_VERBOSE + 1)
>
>  struct tracefs_options_mask;
> -bool tracefs_option_is_set(struct tracefs_options_mask *options,
> +bool tracefs_option_is_set(const struct tracefs_options_mask *options,
>                            enum tracefs_option_id id);
> -struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
> +const struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
>  bool tracefs_option_is_supported(struct tracefs_instance *instance, enum tracefs_option_id id);
> -struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
> +const struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
>  bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_option_id id);
>  int tracefs_option_enable(struct tracefs_instance *instance, enum tracefs_option_id id);
>  int tracefs_option_diasble(struct tracefs_instance *instance, enum tracefs_option_id id);
> diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
> index 49645eb..9cb4b6d 100644
> --- a/src/tracefs-instance.c
> +++ b/src/tracefs-instance.c
> @@ -27,6 +27,8 @@ struct tracefs_instance {
>         char    *trace_dir;
>         char    *name;
>         int     flags;
> +       struct tracefs_options_mask     supported_opts;
> +       struct tracefs_options_mask     enabled_opts;
>  };
>
>  /**
> @@ -695,9 +697,8 @@ static struct tracefs_options_mask *trace_get_options(struct tracefs_instance *i
>         DIR *dir = NULL;
>         long long val;
>
> -       bitmask = calloc(1, sizeof(struct tracefs_options_mask));
> -       if (!bitmask)
> -               return NULL;
> +       bitmask = enabled? &instance->enabled_opts : &instance->supported_opts;

This makes the API not thread safe. There should be no problem with
supported options, as they cannot be changed at runtime. I think it is
OK to limit the APIs , as I see no use case to call them from multiple
threads on the same instance, but this should be described in the
documentation.

> +
>         dname = tracefs_instance_get_file(instance, "options");
>         if (!dname)
>                 goto error;
> @@ -727,7 +728,6 @@ error:
>         if (dir)
>                 closedir(dir);
>         tracefs_put_tracing_file(dname);
> -       free(bitmask);
>         return NULL;
>  }
>
> @@ -735,10 +735,10 @@ error:
>   * tracefs_options_get_supported - Get all supported trace options in given instance
>   * @instance: ftrace instance, can be NULL for the top instance
>   *
> - * Returns allocated bitmask structure with all trace options, supported in given
> - * instance, or NULL in case of an error. The returned structure must be freed with free()
> + * Returns bitmask structure with all trace options, supported in given instance,
> + * or NULL in case of an error.
>   */
> -struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance)
> +const struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance)
>  {
>         return trace_get_options(instance, false);

As supported options cannot be changed at runtime, they can be read
only once. The next calls can return the already initialised bitmask
with supported options.

>  }
> @@ -747,10 +747,10 @@ struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instan
>   * tracefs_options_get_enabled - Get all currently enabled trace options in given instance
>   * @instance: ftrace instance, can be NULL for the top instance
>   *
> - * Returns allocated bitmask structure with all trace options, enabled in given
> - * instance, or NULL in case of an error. The returned structure must be freed with free()
> + * Returns allocated bitmask structure with all trace options, enabled in given instance,
> + * or NULL in case of an error.
>   */
> -struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance)
> +const struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance)
>  {
>         return trace_get_options(instance, true);
>  }
> @@ -758,7 +758,7 @@ struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance
>  static int trace_config_option(struct tracefs_instance *instance,
>                                enum tracefs_option_id id, bool set)
>  {
> -       char *set_str = set ? "1" : "0";
> +       const char *set_str = set ? "1" : "0";
>         char file[PATH_MAX];
>         const char *name;
>
> @@ -846,7 +846,7 @@ bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_o
>   * Returns true if an option with given id is set in the bitmask,
>   * false if it is not set.
>   */
> -bool tracefs_option_is_set(struct tracefs_options_mask *options,
> +bool tracefs_option_is_set(const struct tracefs_options_mask *options,
>                            enum tracefs_option_id id)
>  {
>         if (id > TRACEFS_OPTION_INVALID)
> --
> 2.27.0
>


-- 
Tzvetomir (Ceco) Stoyanov
VMware Open Source Technology Center

Re: [PATCH 5/6] libtracefs: Option's bit masks to be owned by the instance

[Yordan Karadzhov]

On 5.04.21 г. 13:50, Tzvetomir Stoyanov wrote:
> On Fri, Apr 2, 2021 at 4:20 PM Yordan Karadzhov (VMware)
> <y.karadz@gmail.com> wrote:
>> If the instance owns two mask objects, we no longer need to
>> dynamically allocate memory in tracefs_options_get_supported() and
>> tracefs_options_get_enabled(). This will simplify the code on the
>> caller side, since the user is no longer responsible for freeing
>> those masks.
>>
>> Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
>> ---
>>   Documentation/libtracefs-option-get.txt |  4 +---
>>   include/tracefs.h                       |  6 +++---
>>   src/tracefs-instance.c                  | 24 ++++++++++++------------
>>   3 files changed, 16 insertions(+), 18 deletions(-)
>>
>> diff --git a/Documentation/libtracefs-option-get.txt b/Documentation/libtracefs-option-get.txt
>> index 9b3cb56..3290f24 100644
>> --- a/Documentation/libtracefs-option-get.txt
>> +++ b/Documentation/libtracefs-option-get.txt
>> @@ -52,14 +52,13 @@ EXAMPLE
>>   --
>>   #include <tracefs.h>
>>   ...
>> -struct tracefs_options_mask *options;
>> +const struct tracefs_options_mask *options;
>>   ...
>>   options = tracefs_options_get_supported(NULL);
>>   if (!options) {
>>          /* Failed to get supported options */
>>   } else {
>>          ...
>> -       free(options);
>>   }
>>   ..
> The description of the return value of tracefs_options_get_supported()
> and tracefs_options_get_enabled() should be changed also, as it
> suggests to free the return value;
>
>>   options = tracefs_options_get_enabled(NULL);
>> @@ -67,7 +66,6 @@ if (!options) {
>>          /* Failed to get options, enabled in the top instance */
>>   } else {
>>          ...
>> -       free(options);
>>   }
>>   ...
>>
>> diff --git a/include/tracefs.h b/include/tracefs.h
>> index 0665e8d..9efa91a 100644
>> --- a/include/tracefs.h
>> +++ b/include/tracefs.h
>> @@ -132,11 +132,11 @@ enum tracefs_option_id {
>>   #define TRACEFS_OPTION_MAX (TRACEFS_OPTION_VERBOSE + 1)
>>
>>   struct tracefs_options_mask;
>> -bool tracefs_option_is_set(struct tracefs_options_mask *options,
>> +bool tracefs_option_is_set(const struct tracefs_options_mask *options,
>>                             enum tracefs_option_id id);
>> -struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
>> +const struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
>>   bool tracefs_option_is_supported(struct tracefs_instance *instance, enum tracefs_option_id id);
>> -struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
>> +const struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
>>   bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_option_id id);
>>   int tracefs_option_enable(struct tracefs_instance *instance, enum tracefs_option_id id);
>>   int tracefs_option_diasble(struct tracefs_instance *instance, enum tracefs_option_id id);
>> diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
>> index 49645eb..9cb4b6d 100644
>> --- a/src/tracefs-instance.c
>> +++ b/src/tracefs-instance.c
>> @@ -27,6 +27,8 @@ struct tracefs_instance {
>>          char    *trace_dir;
>>          char    *name;
>>          int     flags;
>> +       struct tracefs_options_mask     supported_opts;
>> +       struct tracefs_options_mask     enabled_opts;
>>   };
>>
>>   /**
>> @@ -695,9 +697,8 @@ static struct tracefs_options_mask *trace_get_options(struct tracefs_instance *i
>>          DIR *dir = NULL;
>>          long long val;
>>
>> -       bitmask = calloc(1, sizeof(struct tracefs_options_mask));
>> -       if (!bitmask)
>> -               return NULL;
>> +       bitmask = enabled? &instance->enabled_opts : &instance->supported_opts;
> This makes the API not thread safe. There should be no problem with
> supported options, as they cannot be changed at runtime. I think it is
> OK to limit the APIs , as I see no use case to call them from multiple
> threads on the same instance, but this should be described in the
> documentation.

Discussing is this API is thread safe or not is not really relevant. 
Even if you make tracefs_options_get_enabled() thread safe, this does 
not change anything since the options can be already changed by the time 
when you examine the bits of the mask.


>
>> +
>>          dname = tracefs_instance_get_file(instance, "options");
>>          if (!dname)
>>                  goto error;
>> @@ -727,7 +728,6 @@ error:
>>          if (dir)
>>                  closedir(dir);
>>          tracefs_put_tracing_file(dname);
>> -       free(bitmask);
>>          return NULL;
>>   }
>>
>> @@ -735,10 +735,10 @@ error:
>>    * tracefs_options_get_supported - Get all supported trace options in given instance
>>    * @instance: ftrace instance, can be NULL for the top instance
>>    *
>> - * Returns allocated bitmask structure with all trace options, supported in given
>> - * instance, or NULL in case of an error. The returned structure must be freed with free()
>> + * Returns bitmask structure with all trace options, supported in given instance,
>> + * or NULL in case of an error.
>>    */
>> -struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance)
>> +const struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance)
>>   {
>>          return trace_get_options(instance, false);
> As supported options cannot be changed at runtime, they can be read
> only once. The next calls can return the already initialised bitmask
> with supported options.

If you already have the mask, you do not need to call this function 
second time.

May be if the user intentionally calls the function again, we should 
allow him to regenerate the mask.

What do you think?

Thanks!

Yordan

>
>>   }
>> @@ -747,10 +747,10 @@ struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instan
>>    * tracefs_options_get_enabled - Get all currently enabled trace options in given instance
>>    * @instance: ftrace instance, can be NULL for the top instance
>>    *
>> - * Returns allocated bitmask structure with all trace options, enabled in given
>> - * instance, or NULL in case of an error. The returned structure must be freed with free()
>> + * Returns allocated bitmask structure with all trace options, enabled in given instance,
>> + * or NULL in case of an error.
>>    */
>> -struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance)
>> +const struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance)
>>   {
>>          return trace_get_options(instance, true);
>>   }
>> @@ -758,7 +758,7 @@ struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance
>>   static int trace_config_option(struct tracefs_instance *instance,
>>                                 enum tracefs_option_id id, bool set)
>>   {
>> -       char *set_str = set ? "1" : "0";
>> +       const char *set_str = set ? "1" : "0";
>>          char file[PATH_MAX];
>>          const char *name;
>>
>> @@ -846,7 +846,7 @@ bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_o
>>    * Returns true if an option with given id is set in the bitmask,
>>    * false if it is not set.
>>    */
>> -bool tracefs_option_is_set(struct tracefs_options_mask *options,
>> +bool tracefs_option_is_set(const struct tracefs_options_mask *options,
>>                             enum tracefs_option_id id)
>>   {
>>          if (id > TRACEFS_OPTION_INVALID)
>> --
>> 2.27.0
>>
>

Re: [PATCH 5/6] libtracefs: Option's bit masks to be owned by the instance

[Steven Rostedt]

On Mon, 5 Apr 2021 18:01:41 +0300
Yordan Karadzhov <y.karadz@gmail.com> wrote:

> > This makes the API not thread safe. There should be no problem with
> > supported options, as they cannot be changed at runtime. I think it is
> > OK to limit the APIs , as I see no use case to call them from multiple
> > threads on the same instance, but this should be described in the
> > documentation.  
> 
> Discussing is this API is thread safe or not is not really relevant. 
> Even if you make tracefs_options_get_enabled() thread safe, this does 
> not change anything since the options can be already changed by the time 
> when you examine the bits of the mask.

You are correct, but you also do not want the update of the bitmask to be
corrupted. Thus I think a pthread_mutex() should be added to the updating
of the value, such that we don't have a read/modify/write corruption. Sure
the reader of the mask may get some stale data if its being updated. But it
shouldn't get corrupted data.


void tracefs_option_set(struct tracefs_options_mask *options, enum tracefs_option_id id)
{
	if (options && id > TRACEFS_OPTION_INVALID)
		options->mask |= (1ULL << (id - 1));
}

If two threads are doing this to the same mask, you can have an option set
that gets cleared by another writer, and even though the option is set
after the call, it will be clear in the mask. That is, it's not stale data,
it's incorrect data. That is, the readers after that corruption will get an
option not set, even though it is.

-- Steve

Re: [PATCH 5/6] libtracefs: Option's bit masks to be owned by the instance

[Tzvetomir Stoyanov]

On Fri, Apr 2, 2021 at 4:20 PM Yordan Karadzhov (VMware)
<y.karadz@gmail.com> wrote:
>
> If the instance owns two mask objects, we no longer need to
> dynamically allocate memory in tracefs_options_get_supported() and
> tracefs_options_get_enabled(). This will simplify the code on the
> caller side, since the user is no longer responsible for freeing
> those masks.
>
> Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
> ---
>  Documentation/libtracefs-option-get.txt |  4 +---
>  include/tracefs.h                       |  6 +++---
>  src/tracefs-instance.c                  | 24 ++++++++++++------------
>  3 files changed, 16 insertions(+), 18 deletions(-)
>
> diff --git a/Documentation/libtracefs-option-get.txt b/Documentation/libtracefs-option-get.txt
> index 9b3cb56..3290f24 100644
> --- a/Documentation/libtracefs-option-get.txt
> +++ b/Documentation/libtracefs-option-get.txt
> @@ -52,14 +52,13 @@ EXAMPLE
>  --
>  #include <tracefs.h>
>  ...
> -struct tracefs_options_mask *options;
> +const struct tracefs_options_mask *options;
>  ...
>  options = tracefs_options_get_supported(NULL);
>  if (!options) {
>         /* Failed to get supported options */
>  } else {
>         ...
> -       free(options);
>  }
>  ...
>  options = tracefs_options_get_enabled(NULL);
> @@ -67,7 +66,6 @@ if (!options) {
>         /* Failed to get options, enabled in the top instance */
>  } else {
>         ...
> -       free(options);
>  }
>  ...
>
> diff --git a/include/tracefs.h b/include/tracefs.h
> index 0665e8d..9efa91a 100644
> --- a/include/tracefs.h
> +++ b/include/tracefs.h
> @@ -132,11 +132,11 @@ enum tracefs_option_id {
>  #define TRACEFS_OPTION_MAX (TRACEFS_OPTION_VERBOSE + 1)
>
>  struct tracefs_options_mask;
> -bool tracefs_option_is_set(struct tracefs_options_mask *options,
> +bool tracefs_option_is_set(const struct tracefs_options_mask *options,
>                            enum tracefs_option_id id);
> -struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
> +const struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
>  bool tracefs_option_is_supported(struct tracefs_instance *instance, enum tracefs_option_id id);
> -struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
> +const struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
>  bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_option_id id);
>  int tracefs_option_enable(struct tracefs_instance *instance, enum tracefs_option_id id);
>  int tracefs_option_diasble(struct tracefs_instance *instance, enum tracefs_option_id id);
> diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
> index 49645eb..9cb4b6d 100644
> --- a/src/tracefs-instance.c
> +++ b/src/tracefs-instance.c
> @@ -27,6 +27,8 @@ struct tracefs_instance {
>         char    *trace_dir;
>         char    *name;
>         int     flags;
> +       struct tracefs_options_mask     supported_opts;
> +       struct tracefs_options_mask     enabled_opts;
>  };
>
>  /**
> @@ -695,9 +697,8 @@ static struct tracefs_options_mask *trace_get_options(struct tracefs_instance *i
>         DIR *dir = NULL;
>         long long val;
>
> -       bitmask = calloc(1, sizeof(struct tracefs_options_mask));
> -       if (!bitmask)
> -               return NULL;
> +       bitmask = enabled? &instance->enabled_opts : &instance->supported_opts;

The "instance" argument can be NULL, for the top instance. There
should be global enabled_opts and supported_opts, to be used in that
case.

[..]


-- 
Tzvetomir (Ceco) Stoyanov
VMware Open Source Technology Center

Re: [PATCH 5/6] libtracefs: Option's bit masks to be owned by the instance

[Yordan Karadzhov]

On 5.04.21 г. 13:56, Tzvetomir Stoyanov wrote:
> On Fri, Apr 2, 2021 at 4:20 PM Yordan Karadzhov (VMware)
> <y.karadz@gmail.com> wrote:
>> If the instance owns two mask objects, we no longer need to
>> dynamically allocate memory in tracefs_options_get_supported() and
>> tracefs_options_get_enabled(). This will simplify the code on the
>> caller side, since the user is no longer responsible for freeing
>> those masks.
>>
>> Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
>> ---
>>   Documentation/libtracefs-option-get.txt |  4 +---
>>   include/tracefs.h                       |  6 +++---
>>   src/tracefs-instance.c                  | 24 ++++++++++++------------
>>   3 files changed, 16 insertions(+), 18 deletions(-)
>>
>> diff --git a/Documentation/libtracefs-option-get.txt b/Documentation/libtracefs-option-get.txt
>> index 9b3cb56..3290f24 100644
>> --- a/Documentation/libtracefs-option-get.txt
>> +++ b/Documentation/libtracefs-option-get.txt
>> @@ -52,14 +52,13 @@ EXAMPLE
>>   --
>>   #include <tracefs.h>
>>   ...
>> -struct tracefs_options_mask *options;
>> +const struct tracefs_options_mask *options;
>>   ...
>>   options = tracefs_options_get_supported(NULL);
>>   if (!options) {
>>          /* Failed to get supported options */
>>   } else {
>>          ...
>> -       free(options);
>>   }
>>   ...
>>   options = tracefs_options_get_enabled(NULL);
>> @@ -67,7 +66,6 @@ if (!options) {
>>          /* Failed to get options, enabled in the top instance */
>>   } else {
>>          ...
>> -       free(options);
>>   }
>>   ...
>>
>> diff --git a/include/tracefs.h b/include/tracefs.h
>> index 0665e8d..9efa91a 100644
>> --- a/include/tracefs.h
>> +++ b/include/tracefs.h
>> @@ -132,11 +132,11 @@ enum tracefs_option_id {
>>   #define TRACEFS_OPTION_MAX (TRACEFS_OPTION_VERBOSE + 1)
>>
>>   struct tracefs_options_mask;
>> -bool tracefs_option_is_set(struct tracefs_options_mask *options,
>> +bool tracefs_option_is_set(const struct tracefs_options_mask *options,
>>                             enum tracefs_option_id id);
>> -struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
>> +const struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
>>   bool tracefs_option_is_supported(struct tracefs_instance *instance, enum tracefs_option_id id);
>> -struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
>> +const struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
>>   bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_option_id id);
>>   int tracefs_option_enable(struct tracefs_instance *instance, enum tracefs_option_id id);
>>   int tracefs_option_diasble(struct tracefs_instance *instance, enum tracefs_option_id id);
>> diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
>> index 49645eb..9cb4b6d 100644
>> --- a/src/tracefs-instance.c
>> +++ b/src/tracefs-instance.c
>> @@ -27,6 +27,8 @@ struct tracefs_instance {
>>          char    *trace_dir;
>>          char    *name;
>>          int     flags;
>> +       struct tracefs_options_mask     supported_opts;
>> +       struct tracefs_options_mask     enabled_opts;
>>   };
>>
>>   /**
>> @@ -695,9 +697,8 @@ static struct tracefs_options_mask *trace_get_options(struct tracefs_instance *i
>>          DIR *dir = NULL;
>>          long long val;
>>
>> -       bitmask = calloc(1, sizeof(struct tracefs_options_mask));
>> -       if (!bitmask)
>> -               return NULL;
>> +       bitmask = enabled? &instance->enabled_opts : &instance->supported_opts;
> The "instance" argument can be NULL, for the top instance. There
> should be global enabled_opts and supported_opts, to be used in that
> case.

Yes, this is a bug and I have it in v2 as well. Seems like I will need 
to send v3.

Thanks a lot!

Y.



>
> [..]
>
>

[PATCH 6/6] libtracefs: Rename tracefs_option_is_set()

[Yordan Karadzhov (VMware)]

The old name of the function is potentially confusing. Indeed
the function do not check anything about the option itself (is it
supported or is it enabled). The function only check if inside
the mask the bit that correspond to a given option is set.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 include/tracefs.h      | 4 ++--
 src/tracefs-instance.c | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/tracefs.h b/include/tracefs.h
index 9efa91a..05d2edb 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -132,8 +132,8 @@ enum tracefs_option_id {
 #define TRACEFS_OPTION_MAX (TRACEFS_OPTION_VERBOSE + 1)
 
 struct tracefs_options_mask;
-bool tracefs_option_is_set(const struct tracefs_options_mask *options,
-			   enum tracefs_option_id id);
+bool tracefs_option_mask_is_set(const struct tracefs_options_mask *options,
+				enum tracefs_option_id id);
 const struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
 bool tracefs_option_is_supported(struct tracefs_instance *instance, enum tracefs_option_id id);
 const struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
index 9cb4b6d..f37b024 100644
--- a/src/tracefs-instance.c
+++ b/src/tracefs-instance.c
@@ -839,15 +839,15 @@ bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_o
 }
 
 /**
- * tracefs_option_is_set - Check if given option is set in the bitmask
+ * tracefs_option_mask_is_set - Check if given option is set in the bitmask
  * @options: Options bitmask
  * @id: trace option id
  *
  * Returns true if an option with given id is set in the bitmask,
  * false if it is not set.
  */
-bool tracefs_option_is_set(const struct tracefs_options_mask *options,
-			   enum tracefs_option_id id)
+bool tracefs_option_mask_is_set(const struct tracefs_options_mask *options,
+				enum tracefs_option_id id)
 {
 	if (id > TRACEFS_OPTION_INVALID)
 		return options->mask & (1ULL << (id - 1));
-- 
2.27.0