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Date:   Tue, 24 Oct 2023 15:23:27 -0700
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Subject: [PATCH v3 24/50] perf events: Remove scandir in thread synthesis
From:   Ian Rogers <irogers@google.com>
To:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Ian Rogers <irogers@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Nick Terrell <terrelln@fb.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        Andi Kleen <ak@linux.intel.com>, Leo Yan <leo.yan@linaro.org>,
        Song Liu <song@kernel.org>,
        Sandipan Das <sandipan.das@amd.com>,
        James Clark <james.clark@arm.com>,
        Anshuman Khandual <anshuman.khandual@arm.com>,
        Miguel Ojeda <ojeda@kernel.org>,
        Liam Howlett <liam.howlett@oracle.com>,
        Yang Jihong <yangjihong1@huawei.com>,
        Athira Rajeev <atrajeev@linux.vnet.ibm.com>,
        Kajol Jain <kjain@linux.ibm.com>,
        K Prateek Nayak <kprateek.nayak@amd.com>,
        Sean Christopherson <seanjc@google.com>,
        Yanteng Si <siyanteng@loongson.cn>,
        Ravi Bangoria <ravi.bangoria@amd.com>,
        German Gomez <german.gomez@arm.com>,
        Changbin Du <changbin.du@huawei.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        liuwenyu <liuwenyu7@huawei.com>, linux-kernel@vger.kernel.org,
        linux-perf-users@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

This avoids scanddir reading the directory into memory that's
allocated and instead allocates on the stack.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/synthetic-events.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index a0579c7d7b9e..7cc38f2a0e9e 100644
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -38,6 +38,7 @@
 #include <uapi/linux/mman.h> /* To get things like MAP_HUGETLB even on older libc headers */
 #include <api/fs/fs.h>
 #include <api/io.h>
+#include <api/io_dir.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
@@ -751,10 +752,10 @@ static int __event__synthesize_thread(union perf_event *comm_event,
 				      bool needs_mmap, bool mmap_data)
 {
 	char filename[PATH_MAX];
-	struct dirent **dirent;
+	struct io_dir iod;
+	struct io_dirent64 *dent;
 	pid_t tgid, ppid;
 	int rc = 0;
-	int i, n;
 
 	/* special case: only send one comm event using passed in pid */
 	if (!full) {
@@ -786,16 +787,19 @@ static int __event__synthesize_thread(union perf_event *comm_event,
 	snprintf(filename, sizeof(filename), "%s/proc/%d/task",
 		 machine->root_dir, pid);
 
-	n = scandir(filename, &dirent, filter_task, NULL);
-	if (n < 0)
-		return n;
+	io_dir__init(&iod, open(filename, O_CLOEXEC | O_DIRECTORY | O_RDONLY));
+	if (iod.dirfd < 0)
+		return -1;
 
-	for (i = 0; i < n; i++) {
+	while ((dent = io_dir__readdir(&iod)) != NULL) {
 		char *end;
 		pid_t _pid;
 		bool kernel_thread = false;
 
-		_pid = strtol(dirent[i]->d_name, &end, 10);
+		if (!isdigit(dent->d_name[0]))
+			continue;
+
+		_pid = strtol(dent->d_name, &end, 10);
 		if (*end)
 			continue;
 
@@ -829,9 +833,7 @@ static int __event__synthesize_thread(union perf_event *comm_event,
 		}
 	}
 
-	for (i = 0; i < n; i++)
-		zfree(&dirent[i]);
-	free(dirent);
+	close(iod.dirfd);
 
 	return rc;
 }
-- 
2.42.0.758.gaed0368e0e-goog