Commit b5686363 authored by Darren Hart's avatar Darren Hart Committed by Ingo Molnar
Browse files

futex: clean up futex_(un)lock_pi fault handling 



Impact: cleanup

Some apparently left over cruft code was complicating the fault logic:

Testing if uval != -EFAULT doesn't have any meaning, get_user() sets ret
to either 0 or -EFAULT, there's no need to compare uval, especially not
against EFAULT which it will never be.  This patch removes the superfluous
test and clarifies the comment blocks.

Build and boot tested on an 8way x86_64 system.

Signed-off-by: default avatarDarren Hart <dvhltc@us.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 73500ac5

kernel/futex.c

+12 −14
Original line number Diff line number Diff line
@@ -1565,12 +1565,11 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared, 


 uaddr_faulted:

	/*

	 * We have to r/w  *(int __user *)uaddr, but we can't modify it

	 * non-atomically.  Therefore, if get_user below is not

	 * enough, we need to handle the fault ourselves, while

	 * still holding the mmap_sem.

	 *

	 * ... and hb->lock. :-) --ANK

	 * We have to r/w  *(int __user *)uaddr, and we have to modify it

	 * atomically.  Therefore, if we continue to fault after get_user()

	 * below, we need to handle the fault ourselves, while still holding

	 * the mmap_sem.  This can occur if the uaddr is under contention as

	 * we have to drop the mmap_sem in order to call get_user().

	 */

	queue_unlock(&q, hb);
@@ -1582,7 +1581,7 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared, 
	}



	ret = get_user(uval, uaddr);

	if (!ret && (uval != -EFAULT))

	if (!ret)

		goto retry;



	if (to)
@@ -1676,12 +1675,11 @@ out: 


pi_faulted:

	/*

	 * We have to r/w  *(int __user *)uaddr, but we can't modify it

	 * non-atomically.  Therefore, if get_user below is not

	 * enough, we need to handle the fault ourselves, while

	 * still holding the mmap_sem.

	 *

	 * ... and hb->lock. --ANK

	 * We have to r/w  *(int __user *)uaddr, and we have to modify it

	 * atomically.  Therefore, if we continue to fault after get_user()

	 * below, we need to handle the fault ourselves, while still holding

	 * the mmap_sem.  This can occur if the uaddr is under contention as

	 * we have to drop the mmap_sem in order to call get_user().

	 */

	spin_unlock(&hb->lock);
@@ -1694,7 +1692,7 @@ pi_faulted: 
	}



	ret = get_user(uval, uaddr);

	if (!ret && (uval != -EFAULT))

	if (!ret)

		goto retry;



	return ret;

CRA Git | Maintained and supported by SUSTech CRA and CCSE