Commit 4714d1d3 authored by Ben Blum's avatar Ben Blum Committed by Linus Torvalds
Browse files

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: default avatarBen 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: default avatarPaul 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent dcb3a08e

include/linux/init_task.h

+9 −0
Original line number Diff line number Diff line
@@ -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 @@ extern struct fs_struct init_fs; 
	},								\

	.cred_guard_mutex =						\

		 __MUTEX_INITIALIZER(sig.cred_guard_mutex),		\

	INIT_THREADGROUP_FORK_LOCK(sig)					\

}



extern struct nsproxy init_nsproxy;

include/linux/sched.h

+36 −0
Original line number Diff line number Diff line
@@ -513,6 +513,7 @@ struct thread_group_cputimer { 
	spinlock_t lock;

};



#include <linux/rwsem.h>

struct autogroup;



/*
@@ -632,6 +633,16 @@ struct signal_struct { 
	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 @@ static inline void unlock_task_sighand(struct task_struct *tsk, 
	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)

kernel/fork.c

+10 −0
Original line number Diff line number Diff line
@@ -957,6 +957,10 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 
	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 @@ static struct task_struct *copy_process(unsigned long clone_flags, 
	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 @@ static struct task_struct *copy_process(unsigned long clone_flags, 
	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 @@ bad_fork_cleanup_policy: 
	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);

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