Commit c17112a5 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'core-process-v5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux 

Pull pidfd/waitid updates from Christian Brauner:
 "This contains two features and various tests.

  First, it adds support for waiting on process through pidfds by adding
  the P_PIDFD type to the waitid() syscall. This completes the basic
  functionality of the pidfd api (cf. [1]). In the meantime we also have
  a new adition to the userspace projects that make use of the pidfd
  api. The qt project was nice enough to send a mail pointing out that
  they have a pr up to switch to the pidfd api (cf. [2]).

  Second, this tag contains an extension to the waitid() syscall to make
  it possible to wait on the current process group in a race free manner
  (even though the actual problem is very unlikely) by specifing 0
  together with the P_PGID type. This extension traces back to a
  discussion on the glibc development mailing list.

  There are also a range of tests for the features above. Additionally,
  the test-suite which detected the pidfd-polling race we fixed in [3]
  is included in this tag"

[1] https://lwn.net/Articles/794707/
[2] https://codereview.qt-project.org/c/qt/qtbase/+/108456
[3] commit b191d649 ("pidfd: fix a poll race when setting exit_state")

* tag 'core-process-v5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  waitid: Add support for waiting for the current process group
  tests: add pidfd poll tests
  tests: move common definitions and functions into pidfd.h
  pidfd: add pidfd_wait tests
  pidfd: add P_PIDFD to waitid()
parents 4d856f72 821cc7b0

include/linux/pid.h

+4 −0
Original line number Diff line number Diff line
@@ -72,6 +72,10 @@ extern struct pid init_struct_pid; 


extern const struct file_operations pidfd_fops;



struct file;



extern struct pid *pidfd_pid(const struct file *file);



static inline struct pid *get_pid(struct pid *pid)

{

	if (pid)

include/uapi/linux/wait.h

+1 −0
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#define P_ALL		0

#define P_PID		1

#define P_PGID		2

#define P_PIDFD		3





#endif /* _UAPI_LINUX_WAIT_H */

kernel/exit.c

+34 −4
Original line number Diff line number Diff line
@@ -1554,6 +1554,23 @@ end: 
	return retval;

}



static struct pid *pidfd_get_pid(unsigned int fd)

{

	struct fd f;

	struct pid *pid;



	f = fdget(fd);

	if (!f.file)

		return ERR_PTR(-EBADF);



	pid = pidfd_pid(f.file);

	if (!IS_ERR(pid))

		get_pid(pid);



	fdput(f);

	return pid;

}



static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,

			  int options, struct rusage *ru)

{
@@ -1576,19 +1593,32 @@ static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop, 
		type = PIDTYPE_PID;

		if (upid <= 0)

			return -EINVAL;



		pid = find_get_pid(upid);

		break;

	case P_PGID:

		type = PIDTYPE_PGID;

		if (upid <= 0)

		if (upid < 0)

			return -EINVAL;



		if (upid)

			pid = find_get_pid(upid);

		else

			pid = get_task_pid(current, PIDTYPE_PGID);

		break;

	case P_PIDFD:

		type = PIDTYPE_PID;

		if (upid < 0)

			return -EINVAL;



		pid = pidfd_get_pid(upid);

		if (IS_ERR(pid))

			return PTR_ERR(pid);

		break;

	default:

		return -EINVAL;

	}



	if (type < PIDTYPE_MAX)

		pid = find_get_pid(upid);



	wo.wo_type	= type;

	wo.wo_pid	= pid;

	wo.wo_flags	= options;

kernel/fork.c

+8 −0
Original line number Diff line number Diff line
@@ -1690,6 +1690,14 @@ static inline void rcu_copy_process(struct task_struct *p) 
#endif /* #ifdef CONFIG_TASKS_RCU */

}



struct pid *pidfd_pid(const struct file *file)

{

	if (file->f_op == &pidfd_fops)

		return file->private_data;



	return ERR_PTR(-EBADF);

}



static int pidfd_release(struct inode *inode, struct file *file)

{

	struct pid *pid = file->private_data;

kernel/signal.c

+5 −2
Original line number Diff line number Diff line
@@ -3678,8 +3678,11 @@ static int copy_siginfo_from_user_any(kernel_siginfo_t *kinfo, siginfo_t *info) 


static struct pid *pidfd_to_pid(const struct file *file)

{

	if (file->f_op == &pidfd_fops)

		return file->private_data;

	struct pid *pid;



	pid = pidfd_pid(file);

	if (!IS_ERR(pid))

		return pid;



	return tgid_pidfd_to_pid(file);

}

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