From: Michael Tremer <michael.tremer@ipfire.org>
Date: Sat, 27 Mar 2021 16:39:19 +0000 (+0000)
Subject: cgroups: Implement attaching/detaching processes
X-Git-Tag: 0.9.28~1285^2~456
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4630031cdc204a239c13ed0bb88e640f2dffd882;p=pakfire.git

cgroups: Implement attaching/detaching processes

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
---

diff --git a/src/libpakfire/cgroup.c b/src/libpakfire/cgroup.c
index 84ab8eba1..2dfe2cbd0 100644
--- a/src/libpakfire/cgroup.c
+++ b/src/libpakfire/cgroup.c
@@ -287,3 +287,71 @@ int pakfire_cgroup_destroy(Pakfire pakfire, const char* group) {
 
 	return 0;
 }
+
+int pakfire_cgroup_attach(Pakfire pakfire, const char* group, pid_t pid) {
+	int r = pakfire_cgroup_fprintf(pakfire, group, "cgroup.procs", "%d", pid);
+	if (r < 0) {
+		ERROR(pakfire, "Could not attach process %d to cgroup %s: %s\n",
+			pid, group, strerror(errno));
+		return r;
+	}
+
+	DEBUG(pakfire, "Attached process %d to cgroup %s\n", pid, group);
+	return 0;
+}
+
+int pakfire_cgroup_detach(Pakfire pakfire, const char* group, pid_t pid) {
+	char* parent = pakfire_cgroup_parent_name(group);
+	if (!parent)
+		return EINVAL;
+
+	while (parent) {
+		int r = pakfire_cgroup_attach(pakfire, parent, pid);
+
+		// Break on success
+		if (r == 0) {
+			free(parent);
+			return 0;
+		}
+
+		// Move on to the next parent group
+		char* p = parent;
+		parent = pakfire_cgroup_parent_name(p);
+		free(p);
+	}
+
+	ERROR(pakfire, "Could not detach process %d from %s\n", pid, group);
+	return 1;
+}
+
+static ssize_t pakfire_cgroup_procs_callback(Pakfire pakfire, const char* group,
+		int (*func)(Pakfire pakfire, pid_t pid)) {
+	FILE* f = pakfire_cgroup_fopen(pakfire, group, "cgroup.procs", "r");
+	if (!f)
+		return -1;
+
+	ssize_t num_processes = 0;
+
+	char* line = NULL;
+	size_t l = 0;
+
+	while (1) {
+		ssize_t bytes_read = getline(&line, &l, f);
+		if (bytes_read < 0)
+			break;
+
+		// Increment process counter
+		num_processes++;
+
+		DEBUG(pakfire, "Read line %s\n", line);
+	}
+
+	fclose(f);
+
+	// Returns the number of processes
+	return num_processes;
+}
+
+ssize_t pakfire_cgroup_num_processes(Pakfire pakfire, const char* group) {
+	return pakfire_cgroup_procs_callback(pakfire, group, NULL);
+}
diff --git a/src/libpakfire/include/pakfire/cgroup.h b/src/libpakfire/include/pakfire/cgroup.h
index 32c0f551e..e9766a676 100644
--- a/src/libpakfire/include/pakfire/cgroup.h
+++ b/src/libpakfire/include/pakfire/cgroup.h
@@ -23,11 +23,18 @@
 
 #ifdef PAKFIRE_PRIVATE
 
+#include <sys/types.h>
+
 #include <pakfire/types.h>
 
 int pakfire_cgroup_create(Pakfire pakfire, const char* group);
 int pakfire_cgroup_destroy(Pakfire pakfire, const char* group);
 
+int pakfire_cgroup_attach(Pakfire pakfire, const char* group, pid_t pid);
+int pakfire_cgroup_detach(Pakfire pakfire, const char* group, pid_t pid);
+
+ssize_t pakfire_cgroup_num_processes(Pakfire pakfire, const char* group);
+
 #endif
 
 #endif /* PAKFIRE_CGROUP_H */
diff --git a/tests/libpakfire/cgroup.c b/tests/libpakfire/cgroup.c
index 04a41661a..f6cdb7b1b 100644
--- a/tests/libpakfire/cgroup.c
+++ b/tests/libpakfire/cgroup.c
@@ -18,6 +18,9 @@
 #                                                                             #
 #############################################################################*/
 
+#include <sys/types.h>
+#include <unistd.h>
+
 #include <pakfire/cgroup.h>
 
 #include "../testsuite.h"
@@ -34,8 +37,48 @@ static int test_create_and_destroy(const struct test* t) {
 	return EXIT_SUCCESS;
 }
 
+static int test_attach(const struct test* t) {
+	ssize_t num_processes;
+
+	// Fetch the PID of the test process
+	pid_t pid = getpid();
+
+	printf("This process's PID: %d\n", pid);
+
+	ASSERT_SUCCESS(
+		pakfire_cgroup_create(t->pakfire, "pakfire/test")
+	);
+
+	// Check that there are no processes in this group
+	num_processes = pakfire_cgroup_num_processes(t->pakfire, "pakfire/test");
+	ASSERT(num_processes == 0);
+
+	ASSERT_SUCCESS(
+		pakfire_cgroup_attach(t->pakfire, "pakfire/test", pid)
+	);
+
+	// Check that there is exactly one process in this group
+	num_processes = pakfire_cgroup_num_processes(t->pakfire, "pakfire/test");
+	ASSERT(num_processes == 1);
+
+	ASSERT_SUCCESS(
+		pakfire_cgroup_detach(t->pakfire, "pakfire/test", pid)
+	);
+
+	// Check that there are no processes in this group
+	num_processes = pakfire_cgroup_num_processes(t->pakfire, "pakfire/test");
+	ASSERT(num_processes == 0);
+
+	ASSERT_SUCCESS(
+		pakfire_cgroup_destroy(t->pakfire, "pakfire/test")
+	);
+
+	return EXIT_SUCCESS;
+}
+
 int main(int argc, char** argv) {
 	testsuite_add_test(test_create_and_destroy);
+	testsuite_add_test(test_attach);
 
 	return testsuite_run();
 }