cgroups: read-write lock CLONE_THREAD forking per threadgroup
Adds functionality to read/write lock CLONE_THREAD fork()ing per-threadgroup
Add an rwsem that lives in a threadgroup's signal_struct that's taken for
reading in the fork path, under CONFIG_CGROUPS. If another part of the
kernel later wants to use such a locking mechanism, the CONFIG_CGROUPS
ifdefs should be changed to a higher-up flag that CGROUPS and the other
system would both depend on.
This is a pre-patch for cgroup-procs-write.patch.
Signed-off-by: Ben Blum <bblum@andrew.cmu.edu>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Reviewed-by: Paul Menage <menage@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index bafc58c..580f70c 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -22,6 +22,14 @@
extern struct files_struct init_files;
extern struct fs_struct init_fs;
+#ifdef CONFIG_CGROUPS
+#define INIT_THREADGROUP_FORK_LOCK(sig) \
+ .threadgroup_fork_lock = \
+ __RWSEM_INITIALIZER(sig.threadgroup_fork_lock),
+#else
+#define INIT_THREADGROUP_FORK_LOCK(sig)
+#endif
+
#define INIT_SIGNALS(sig) { \
.nr_threads = 1, \
.wait_chldexit = __WAIT_QUEUE_HEAD_INITIALIZER(sig.wait_chldexit),\
@@ -38,6 +46,7 @@
}, \
.cred_guard_mutex = \
__MUTEX_INITIALIZER(sig.cred_guard_mutex), \
+ INIT_THREADGROUP_FORK_LOCK(sig) \
}
extern struct nsproxy init_nsproxy;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f18300e..dc88712 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -513,6 +513,7 @@
spinlock_t lock;
};
+#include <linux/rwsem.h>
struct autogroup;
/*
@@ -632,6 +633,16 @@
unsigned audit_tty;
struct tty_audit_buf *tty_audit_buf;
#endif
+#ifdef CONFIG_CGROUPS
+ /*
+ * The threadgroup_fork_lock prevents threads from forking with
+ * CLONE_THREAD while held for writing. Use this for fork-sensitive
+ * threadgroup-wide operations. It's taken for reading in fork.c in
+ * copy_process().
+ * Currently only needed write-side by cgroups.
+ */
+ struct rw_semaphore threadgroup_fork_lock;
+#endif
int oom_adj; /* OOM kill score adjustment (bit shift) */
int oom_score_adj; /* OOM kill score adjustment */
@@ -2323,6 +2334,31 @@
spin_unlock_irqrestore(&tsk->sighand->siglock, *flags);
}
+/* See the declaration of threadgroup_fork_lock in signal_struct. */
+#ifdef CONFIG_CGROUPS
+static inline void threadgroup_fork_read_lock(struct task_struct *tsk)
+{
+ down_read(&tsk->signal->threadgroup_fork_lock);
+}
+static inline void threadgroup_fork_read_unlock(struct task_struct *tsk)
+{
+ up_read(&tsk->signal->threadgroup_fork_lock);
+}
+static inline void threadgroup_fork_write_lock(struct task_struct *tsk)
+{
+ down_write(&tsk->signal->threadgroup_fork_lock);
+}
+static inline void threadgroup_fork_write_unlock(struct task_struct *tsk)
+{
+ up_write(&tsk->signal->threadgroup_fork_lock);
+}
+#else
+static inline void threadgroup_fork_read_lock(struct task_struct *tsk) {}
+static inline void threadgroup_fork_read_unlock(struct task_struct *tsk) {}
+static inline void threadgroup_fork_write_lock(struct task_struct *tsk) {}
+static inline void threadgroup_fork_write_unlock(struct task_struct *tsk) {}
+#endif
+
#ifndef __HAVE_THREAD_FUNCTIONS
#define task_thread_info(task) ((struct thread_info *)(task)->stack)
diff --git a/kernel/fork.c b/kernel/fork.c
index 8e7e135..1fa9d94 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -957,6 +957,10 @@
tty_audit_fork(sig);
sched_autogroup_fork(sig);
+#ifdef CONFIG_CGROUPS
+ init_rwsem(&sig->threadgroup_fork_lock);
+#endif
+
sig->oom_adj = current->signal->oom_adj;
sig->oom_score_adj = current->signal->oom_score_adj;
sig->oom_score_adj_min = current->signal->oom_score_adj_min;
@@ -1138,6 +1142,8 @@
monotonic_to_bootbased(&p->real_start_time);
p->io_context = NULL;
p->audit_context = NULL;
+ if (clone_flags & CLONE_THREAD)
+ threadgroup_fork_read_lock(current);
cgroup_fork(p);
#ifdef CONFIG_NUMA
p->mempolicy = mpol_dup(p->mempolicy);
@@ -1342,6 +1348,8 @@
write_unlock_irq(&tasklist_lock);
proc_fork_connector(p);
cgroup_post_fork(p);
+ if (clone_flags & CLONE_THREAD)
+ threadgroup_fork_read_unlock(current);
perf_event_fork(p);
return p;
@@ -1380,6 +1388,8 @@
mpol_put(p->mempolicy);
bad_fork_cleanup_cgroup:
#endif
+ if (clone_flags & CLONE_THREAD)
+ threadgroup_fork_read_unlock(current);
cgroup_exit(p, cgroup_callbacks_done);
delayacct_tsk_free(p);
module_put(task_thread_info(p)->exec_domain->module);