linux-kernel - [PATCH RFC 0/2] Reenable might_sleep() checks for might

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Date:	Thu, 27 Nov 2014 18:10:15 +0100
From:	David Hildenbrand <dahi@...ux.vnet.ibm.com>
To:	linuxppc-dev@...ts.ozlabs.org, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	benh@...nel.crashing.org, paulus@...ba.org,
	akpm@...ux-foundation.org, heiko.carstens@...ibm.com,
	dahi@...ux.vnet.ibm.com, schwidefsky@...ibm.com,
	borntraeger@...ibm.com, mst@...hat.com, tglx@...utronix.de,
	David.Laight@...LAB.COM
Subject: [PATCH RFC 0/2] Reenable might_sleep() checks for might_fault() when atomic

Simple prototype to enable might_sleep() checks in might_fault(), avoiding false
positives for scenarios involving explicit pagefault_disable().

So this should work:
	spin_lock(&lock); /* also if left away */
	pagefault_disable()
	rc = copy_to_user(...)
	pagefault_enable();
	spin_unlock(&lock); /*

And this should report a warning again:
	spin_lock(&lock);
	rc = copy_to_user(...);
	spin_unlock(&lock);

Still missing:
- Split of preempt documentation update + preempt_active define reshuffle
- Debug version to test for over/underflows
- Change documentation of user access methods to reflect the real behavior
- Don't touch the preempt counter, only the pagefault disable counter (future
  work)

David Hildenbrand (2):
  preempt: track pagefault_disable() calls in the preempt counter
  mm, sched: trigger might_sleep() in might_fault() when pagefaults are
    disabled

 include/linux/kernel.h       |  9 +++++++--
 include/linux/preempt_mask.h | 24 +++++++++++++++++++-----
 include/linux/uaccess.h      | 21 ++++++++++++++-------
 mm/memory.c                  | 15 ++++-----------
 4 files changed, 44 insertions(+), 25 deletions(-)

-- 
1.8.5.5

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