Commit 13ca6287 authored by Ian Rogers's avatar Ian Rogers Committed by Arnaldo Carvalho de Melo
Browse files

perf comm: Add reference count checking to 'struct comm_str' 



Reference count checking of an rbtree is troublesome as each pointer
should have a reference, switch to using a sorted array.

Remove an indirection by embedding the reference count with the string.

Use pthread_once to safely initialize the comm_strs and reader writer
mutex.

Signed-off-by: default avatarIan Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Ben Gainey <ben.gainey@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Li Dong <lidong@vivo.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Paran Lee <p4ranlee@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Sun Haiyong <sunhaiyong@loongson.cn>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Yanteng Si <siyanteng@loongson.cn>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Link: https://lore.kernel.org/r/20240507183545.1236093-6-irogers@google.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent a8cd4766

tools/perf/util/comm.c

+126 −70
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#include "comm.h"

#include <errno.h>

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

#include <internal/rc_check.h>

#include <linux/refcount.h>

#include <linux/rbtree.h>

#include <linux/zalloc.h>

#include "rwsem.h"



struct comm_str {

	char *str;

	struct rb_node rb_node;

DECLARE_RC_STRUCT(comm_str) {

	refcount_t refcnt;

	char str[];

};



/* Should perhaps be moved to struct machine */

static struct rb_root comm_str_root;

static struct rw_semaphore comm_str_lock = {.lock = PTHREAD_RWLOCK_INITIALIZER,};

static struct comm_strs {

	struct rw_semaphore lock;

	struct comm_str **strs;

	int num_strs;

	int capacity;

} _comm_strs;



static void comm_strs__init(void)

{

	init_rwsem(&_comm_strs.lock);

	_comm_strs.capacity = 16;

	_comm_strs.num_strs = 0;

	_comm_strs.strs = calloc(16, sizeof(*_comm_strs.strs));

}



static struct comm_strs *comm_strs__get(void)

{

	static pthread_once_t comm_strs_type_once = PTHREAD_ONCE_INIT;



	pthread_once(&comm_strs_type_once, comm_strs__init);



	return &_comm_strs;

}



static refcount_t *comm_str__refcnt(struct comm_str *cs)

{

	return &RC_CHK_ACCESS(cs)->refcnt;

}



static const char *comm_str__str(const struct comm_str *cs)

{

	return &RC_CHK_ACCESS(cs)->str[0];

}



static struct comm_str *comm_str__get(struct comm_str *cs)

{

	if (cs && refcount_inc_not_zero(&cs->refcnt))

		return cs;

	struct comm_str *result;



	return NULL;

	if (RC_CHK_GET(result, cs))

		refcount_inc_not_zero(comm_str__refcnt(cs));



	return result;

}



static void comm_str__put(struct comm_str *cs)

{

	if (cs && refcount_dec_and_test(&cs->refcnt)) {

		down_write(&comm_str_lock);

		rb_erase(&cs->rb_node, &comm_str_root);

		up_write(&comm_str_lock);

		zfree(&cs->str);

		free(cs);

	if (cs && refcount_dec_and_test(comm_str__refcnt(cs))) {

		struct comm_strs *comm_strs = comm_strs__get();

		int i;



		down_write(&comm_strs->lock);

		for (i = 0; i < comm_strs->num_strs; i++) {

			if (comm_strs->strs[i] == cs)

				break;

		}

		for (; i < comm_strs->num_strs - 1; i++)

			comm_strs->strs[i] = comm_strs->strs[i + 1];



		comm_strs->num_strs--;

		up_write(&comm_strs->lock);

		RC_CHK_FREE(cs);

	} else {

		RC_CHK_PUT(cs);

	}

}



static struct comm_str *comm_str__alloc(const char *str)

static struct comm_str *comm_str__new(const char *str)

{

	struct comm_str *cs;

	struct comm_str *result = NULL;

	RC_STRUCT(comm_str) *cs;



	cs = zalloc(sizeof(*cs));

	if (!cs)

		return NULL;

	cs = malloc(sizeof(*cs) + strlen(str) + 1);

	if (ADD_RC_CHK(result, cs)) {

		refcount_set(comm_str__refcnt(result), 1);

		strcpy(&cs->str[0], str);

	}

	return result;

}



	cs->str = strdup(str);

	if (!cs->str) {

		free(cs);

		return NULL;

static int comm_str__cmp(const void *_lhs, const void *_rhs)

{

	const struct comm_str *lhs = *(const struct comm_str * const *)_lhs;

	const struct comm_str *rhs = *(const struct comm_str * const *)_rhs;



	return strcmp(comm_str__str(lhs), comm_str__str(rhs));

}



	refcount_set(&cs->refcnt, 1);

static int comm_str__search(const void *_key, const void *_member)

{

	const char *key = _key;

	const struct comm_str *member = *(const struct comm_str * const *)_member;



	return cs;

	return strcmp(key, comm_str__str(member));

}



static

struct comm_str *__comm_str__findnew(const char *str, struct rb_root *root)

static struct comm_str *__comm_strs__find(struct comm_strs *comm_strs, const char *str)

{

	struct rb_node **p = &root->rb_node;

	struct rb_node *parent = NULL;

	struct comm_str *iter, *new;

	int cmp;



	while (*p != NULL) {

		parent = *p;

		iter = rb_entry(parent, struct comm_str, rb_node);



		/*

		 * If we race with comm_str__put, iter->refcnt is 0

		 * and it will be removed within comm_str__put call

		 * shortly, ignore it in this search.

		 */

		cmp = strcmp(str, iter->str);

		if (!cmp && comm_str__get(iter))

			return iter;



		if (cmp < 0)

			p = &(*p)->rb_left;

		else

			p = &(*p)->rb_right;

	}



	new = comm_str__alloc(str);

	if (!new)

		return NULL;

	struct comm_str **result;



	rb_link_node(&new->rb_node, parent, p);

	rb_insert_color(&new->rb_node, root);

	result = bsearch(str, comm_strs->strs, comm_strs->num_strs, sizeof(struct comm_str *),

			 comm_str__search);



	return new;

	if (!result)

		return NULL;



	return comm_str__get(*result);

}



static struct comm_str *comm_str__findnew(const char *str, struct rb_root *root)

static struct comm_str *comm_strs__findnew(const char *str)

{

	struct comm_str *cs;

	struct comm_strs *comm_strs = comm_strs__get();

	struct comm_str *result;



	down_write(&comm_str_lock);

	cs = __comm_str__findnew(str, root);

	up_write(&comm_str_lock);

	if (!comm_strs)

		return NULL;



	return cs;

	down_read(&comm_strs->lock);

	result = __comm_strs__find(comm_strs, str);

	up_read(&comm_strs->lock);

	if (result)

		return result;



	down_write(&comm_strs->lock);

	result = __comm_strs__find(comm_strs, str);

	if (!result) {

		if (comm_strs->num_strs == comm_strs->capacity) {

			struct comm_str **tmp;



			tmp = reallocarray(comm_strs->strs,

					   comm_strs->capacity + 16,

					   sizeof(*comm_strs->strs));

			if (!tmp) {

				up_write(&comm_strs->lock);

				return NULL;

			}

			comm_strs->strs = tmp;

			comm_strs->capacity += 16;

		}

		result = comm_str__new(str);

		if (result) {

			comm_strs->strs[comm_strs->num_strs++] = result;

			qsort(comm_strs->strs, comm_strs->num_strs, sizeof(struct comm_str *),

			      comm_str__cmp);

		}

	}

	up_write(&comm_strs->lock);

	return result;

}



struct comm *comm__new(const char *str, u64 timestamp, bool exec)
@@ -115,7 +171,7 @@ struct comm *comm__new(const char *str, u64 timestamp, bool exec) 
	comm->start = timestamp;

	comm->exec = exec;



	comm->comm_str = comm_str__findnew(str, &comm_str_root);

	comm->comm_str = comm_strs__findnew(str);

	if (!comm->comm_str) {

		free(comm);

		return NULL;
@@ -128,7 +184,7 @@ int comm__override(struct comm *comm, const char *str, u64 timestamp, bool exec) 
{

	struct comm_str *new, *old = comm->comm_str;



	new = comm_str__findnew(str, &comm_str_root);

	new = comm_strs__findnew(str);

	if (!new)

		return -ENOMEM;
@@ -149,5 +205,5 @@ void comm__free(struct comm *comm) 


const char *comm__str(const struct comm *comm)

{

	return comm->comm_str->str;

	return comm_str__str(comm->comm_str);

}