/* Function to determine if a thread group is single threaded or not
 *
 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 * - Derived from security/selinux/hooks.c
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/sched.h>

/*
 * Returns true if the task does not share ->mm with another thread/process.
 */
bool current_is_single_threaded(void)
{
	struct task_struct *task = current;
	struct mm_struct *mm = task->mm;
	struct task_struct *p, *t;
	bool ret;

	if (atomic_read(&task->signal->live) != 1)
		return false;

	if (atomic_read(&mm->mm_users) == 1)
		return true;

	ret = false;
	rcu_read_lock();
	for_each_process(p) {
		if (unlikely(p->flags & PF_KTHREAD))
			continue;
		if (unlikely(p == task->group_leader))
			continue;

		for_each_thread(p, t) {
			if (unlikely(t->mm == mm))
				goto found;
			if (likely(t->mm))
				break;
			/*
			 * t->mm == NULL. Make sure next_thread/next_task
			 * will see other CLONE_VM tasks which might be
			 * forked before exiting.
			 */
			smp_rmb();
		}
	}
	ret = true;
found:
	rcu_read_unlock();

	return ret;
}
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<tr><th>author</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2016-12-12 21:58:13 -0800</td></tr>
<tr><th>committer</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2016-12-12 21:58:13 -0800</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/?id=e7aa8c2eb11ba69b1b69099c3c7bd6be3087b0ba'>e7aa8c2eb11ba69b1b69099c3c7bd6be3087b0ba</a> (<a href='/cgit.cgi/linux/net-next.git/patch/?id=e7aa8c2eb11ba69b1b69099c3c7bd6be3087b0ba'>patch</a>)</td></tr>
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<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/?id=e34bac726d27056081d0250c0e173e4b155aa340'>e34bac726d27056081d0250c0e173e4b155aa340</a> (<a href='/cgit.cgi/linux/net-next.git/diff/?id2=e34bac726d27056081d0250c0e173e4b155aa340'>diff</a>)</td></tr><tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/?id=868c97a846a73e937d835b09b8c885a69df50ec8'>868c97a846a73e937d835b09b8c885a69df50ec8</a> (<a href='/cgit.cgi/linux/net-next.git/diff/?id2=868c97a846a73e937d835b09b8c885a69df50ec8'>diff</a>)</td></tr></table>
<div class='commit-subject'>Merge tag 'docs-4.10' of git://git.lwn.net/linux<span class='decoration'><a class='deco' href='/cgit.cgi/linux/net-next.git/commit/?id=e7aa8c2eb11ba69b1b69099c3c7bd6be3087b0ba'>HEAD</a><a class='branch-deco' href='/cgit.cgi/linux/net-next.git/log/'>master</a></span></div><div class='commit-msg'>Pull documentation update from Jonathan Corbet:
 "These are the documentation changes for 4.10.

  It's another busy cycle for the docs tree, as the sphinx conversion
  continues. Highlights include:

   - Further work on PDF output, which remains a bit of a pain but
     should be more solid now.

   - Five more DocBook template files converted to Sphinx. Only 27 to
     go... Lots of plain-text files have also been converted and
     integrated.

   - Images in binary formats have been replaced with more
     source-friendly versions.

   - Various bits of organizational work, including the renaming of
     various files discussed at the kernel summit.

   - New documentation for the device_link mechanism.

  ... and, of course, lots of typo fixes and small updates"

* tag 'docs-4.10' of git://git.lwn.net/linux: (193 commits)
  dma-buf: Extract dma-buf.rst
  Update Documentation/00-INDEX
  docs: 00-INDEX: document directories/files with no docs
  docs: 00-INDEX: remove non-existing entries
  docs: 00-INDEX: add missing entries for documentation files/dirs
  docs: 00-INDEX: consolidate process/ and admin-guide/ description
  scripts: add a script to check if Documentation/00-INDEX is sane
  Docs: change sh -&gt; awk in REPORTING-BUGS
  Documentation/core-api/device_link: Add initial documentation
  core-api: remove an unexpected unident
  ppc/idle: Add documentation for powersave=off
  Doc: Correct typo, "Introdution" =&gt; "Introduction"
  Documentation/atomic_ops.txt: convert to ReST markup
  Documentation/local_ops.txt: convert to ReST markup
  Documentation/assoc_array.txt: convert to ReST markup
  docs-rst: parse-headers.pl: cleanup the documentation
  docs-rst: fix media cleandocs target
  docs-rst: media/Makefile: reorganize the rules
  docs-rst: media: build SVG from graphviz files
  docs-rst: replace bayer.png by a SVG image
  ...
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/'>Diffstat</a></div><table summary='diffstat' class='diffstat'>