Merge branch 'for-3.9' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup changes from Tejun Heo:
 "Nothing too drastic.

   - Removal of synchronize_rcu() from userland visible paths.

   - Various fixes and cleanups from Li.

   - cgroup_rightmost_descendant() added which will be used by cpuset
     changes (it will be a separate pull request)."

* 'for-3.9' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: fail if monitored file and event_control are in different cgroup
  cgroup: fix cgroup_rmdir() vs close(eventfd) race
  cpuset: fix cpuset_print_task_mems_allowed() vs rename() race
  cgroup: fix exit() vs rmdir() race
  cgroup: remove bogus comments in cgroup_diput()
  cgroup: remove synchronize_rcu() from cgroup_diput()
  cgroup: remove duplicate RCU free on struct cgroup
  sched: remove redundant NULL cgroup check in task_group_path()
  sched: split out css_online/css_offline from tg creation/destruction
  cgroup: initialize cgrp->dentry before css_alloc()
  cgroup: remove a NULL check in cgroup_exit()
  cgroup: fix bogus kernel warnings when cgroup_create() failed
  cgroup: remove synchronize_rcu() from rebind_subsystems()
  cgroup: remove synchronize_rcu() from cgroup_attach_{task|proc}()
  cgroup: use new hashtable implementation
  cgroups: fix cgroup_event_listener error handling
  cgroups: move cgroup_event_listener.c to tools/cgroup
  cgroup: implement cgroup_rightmost_descendant()
  cgroup: remove unused dummy cgroup_fork_callbacks()

tools/Makefile

@@ -3,6 +3,7 @@ include scripts/Makefile.include
 help:
 	@echo 'Possible targets:'
 	@echo ''
+	@echo '  cgroup     - cgroup tools'
 	@echo '  cpupower   - a tool for all things x86 CPU power'
 	@echo '  firewire   - the userspace part of nosy, an IEEE-1394 traffic sniffer'
 	@echo '  lguest     - a minimal 32-bit x86 hypervisor'
@@ -33,7 +34,7 @@ help:
 cpupower: FORCE
 	$(call descend,power/$@)
 
-firewire lguest perf usb virtio vm: FORCE
+cgroup firewire lguest perf usb virtio vm: FORCE
 	$(call descend,$@)
 
 selftests: FORCE
@@ -45,7 +46,7 @@ turbostat x86_energy_perf_policy: FORCE
 cpupower_install:
 	$(call descend,power/$(@:_install=),install)
 
-firewire_install lguest_install perf_install usb_install virtio_install vm_install:
+cgroup_install firewire_install lguest_install perf_install usb_install virtio_install vm_install:
 	$(call descend,$(@:_install=),install)
 
 selftests_install:
@@ -54,14 +55,14 @@ selftests_install:
 turbostat_install x86_energy_perf_policy_install:
 	$(call descend,power/x86/$(@:_install=),install)
 
-install: cpupower_install firewire_install lguest_install perf_install \
-		selftests_install turbostat_install usb_install virtio_install \
-		vm_install x86_energy_perf_policy_install
+install: cgroup_install cpupower_install firewire_install lguest_install \
+		perf_install selftests_install turbostat_install usb_install \
+		virtio_install vm_install x86_energy_perf_policy_install
 
 cpupower_clean:
 	$(call descend,power/cpupower,clean)
 
-firewire_clean lguest_clean perf_clean usb_clean virtio_clean vm_clean:
+cgroup_clean firewire_clean lguest_clean perf_clean usb_clean virtio_clean vm_clean:
 	$(call descend,$(@:_clean=),clean)
 
 selftests_clean:
@@ -70,8 +71,8 @@ selftests_clean:
 turbostat_clean x86_energy_perf_policy_clean:
 	$(call descend,power/x86/$(@:_clean=),clean)
 
-clean: cpupower_clean firewire_clean lguest_clean perf_clean selftests_clean \
-		turbostat_clean usb_clean virtio_clean vm_clean \
-		x86_energy_perf_policy_clean
+clean: cgroup_clean cpupower_clean firewire_clean lguest_clean perf_clean \
+		selftests_clean turbostat_clean usb_clean virtio_clean \
+		vm_clean x86_energy_perf_policy_clean
 
 .PHONY: FORCE

tools/cgroup/.gitignore

@@ -0,0 +1 @@
+cgroup_event_listener

tools/cgroup/Makefile

@@ -0,0 +1,11 @@
+# Makefile for cgroup tools
+
+CC = $(CROSS_COMPILE)gcc
+CFLAGS = -Wall -Wextra
+
+all: cgroup_event_listener
+%: %.c
+	$(CC) $(CFLAGS) -o $@ $^
+
+clean:
+	$(RM) cgroup_event_listener

tools/cgroup/cgroup_event_listener.c

@@ -0,0 +1,82 @@
+/*
+ * cgroup_event_listener.c - Simple listener of cgroup events
+ *
+ * Copyright (C) Kirill A. Shutemov <kirill@shutemov.name>
+ */
+
+#include <assert.h>
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <libgen.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <sys/eventfd.h>
+
+#define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>"
+
+int main(int argc, char **argv)
+{
+	int efd = -1;
+	int cfd = -1;
+	int event_control = -1;
+	char event_control_path[PATH_MAX];
+	char line[LINE_MAX];
+	int ret;
+
+	if (argc != 3)
+		errx(1, "%s", USAGE_STR);
+
+	cfd = open(argv[1], O_RDONLY);
+	if (cfd == -1)
+		err(1, "Cannot open %s", argv[1]);
+
+	ret = snprintf(event_control_path, PATH_MAX, "%s/cgroup.event_control",
+			dirname(argv[1]));
+	if (ret >= PATH_MAX)
+		errx(1, "Path to cgroup.event_control is too long");
+
+	event_control = open(event_control_path, O_WRONLY);
+	if (event_control == -1)
+		err(1, "Cannot open %s", event_control_path);
+
+	efd = eventfd(0, 0);
+	if (efd == -1)
+		err(1, "eventfd() failed");
+
+	ret = snprintf(line, LINE_MAX, "%d %d %s", efd, cfd, argv[2]);
+	if (ret >= LINE_MAX)
+		errx(1, "Arguments string is too long");
+
+	ret = write(event_control, line, strlen(line) + 1);
+	if (ret == -1)
+		err(1, "Cannot write to cgroup.event_control");
+
+	while (1) {
+		uint64_t result;
+
+		ret = read(efd, &result, sizeof(result));
+		if (ret == -1) {
+			if (errno == EINTR)
+				continue;
+			err(1, "Cannot read from eventfd");
+		}
+		assert(ret == sizeof(result));
+
+		ret = access(event_control_path, W_OK);
+		if ((ret == -1) && (errno == ENOENT)) {
+			puts("The cgroup seems to have removed.");
+			break;
+		}
+
+		if (ret == -1)
+			err(1, "cgroup.event_control is not accessible any more");
+
+		printf("%s %s: crossed\n", argv[1], argv[2]);
+	}
+
+	return 0;
+}