core: add support for the "pids" cgroup controller

This adds support for the new "pids" cgroup controller of 4.3 kernels.
It allows accounting the number of tasks in a cgroup and enforcing
limits on it.

This adds two new setting TasksAccounting= and TasksMax= to each unit,
as well as a gloabl option DefaultTasksAccounting=.

This also updated "cgtop" to optionally make use of the new
kernel-provided accounting.

systemctl has been updated to show the number of tasks for each service
if it is available.

This patch also adds correct support for undoing memory limits for units
using a MemoryLimit=infinity syntax. We do the same for TasksMax= now
and hence keep things in sync here.

1 files changed, 33 insertions, 4 deletions

diff --git a/src/core/load-fragment.c b/src/core/load-fragment.c
index 3b02cd8085..07f2770559 100644
--- a/src/core/load-fragment.c
+++ b/src/core/load-fragment.c
@@ -2686,7 +2686,7 @@ int config_parse_memory_limit(
         off_t bytes;
         int r;
 
-        if (isempty(rvalue)) {
+        if (isempty(rvalue) || streq(rvalue, "infinity")) {
                 c->memory_limit = (uint64_t) -1;
                 return 0;
         }
@@ -2694,9 +2694,8 @@ int config_parse_memory_limit(
         assert_cc(sizeof(uint64_t) == sizeof(off_t));
 
         r = parse_size(rvalue, 1024, &bytes);
-        if (r < 0) {
-                log_syntax(unit, LOG_ERR, filename, line, EINVAL,
-                           "Memory limit '%s' invalid. Ignoring.", rvalue);
+        if (r < 0 || bytes < 1) {
+                log_syntax(unit, LOG_ERR, filename, line, EINVAL, "Memory limit '%s' invalid. Ignoring.", rvalue);
                 return 0;
         }
 
@@ -2704,6 +2703,36 @@ int config_parse_memory_limit(
         return 0;
 }
 
+int config_parse_tasks_max(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        CGroupContext *c = data;
+        uint64_t u;
+        int r;
+
+        if (isempty(rvalue) || streq(rvalue, "infinity")) {
+                c->tasks_max = (uint64_t) -1;
+                return 0;
+        }
+
+        r = safe_atou64(rvalue, &u);
+        if (r < 0 || u < 1) {
+                log_syntax(unit, LOG_ERR, filename, line, EINVAL, "Maximum tasks value '%s' invalid. Ignoring.", rvalue);
+                return 0;
+        }
+
+        return 0;
+}
+
 int config_parse_device_allow(
                 const char *unit,
                 const char *filename,