linux-toradex.git/kernel/futex.c, branch v2.6.20.21

[PATCH] FUTEX: Restore the dropped ERSCH fix

2007-08-15T08:02:31+00:00

The return value of futex_find_get_task() needs to be -ESRCH in case
that the search fails. This was part of the original futex fixes and
got accidentally dropped, when the futex-tidy-up patch was split out.

Results in a NULL pointer dereference in case the search fails.

Restore it.

Signed-off-by: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Ulrich Drepper 
Signed-off-by: Chris Wright 
Signed-off-by: Greg Kroah-Hartman

[PATCH] pi-futex: Fix exit races and locking problems

2007-08-15T08:02:26+00:00

1. New entries can be added to tsk->pi_state_list after task completed
   exit_pi_state_list(). The result is memory leakage and deadlocks.

2. handle_mm_fault() is called under spinlock. The result is obvious.

3. results in self-inflicted deadlock inside glibc.
   Sometimes futex_lock_pi returns -ESRCH, when it is not expected
   and glibc enters to for(;;) sleep() to simulate deadlock. This problem
   is quite obvious and I think the patch is right. Though it looks like
   each "if" in futex_lock_pi() got some stupid special case "else if". :-)

4. sometimes futex_lock_pi() returns -EDEADLK,
   when nobody has the lock. The reason is also obvious (see comment
   in the patch), but correct fix is far beyond my comprehension.
   I guess someone already saw this, the chunk:

                        if (rt_mutex_trylock(&q.pi_state->pi_mutex))
                                ret = 0;

   is obviously from the same opera. But it does not work, because the
   rtmutex is really taken at this point: wake_futex_pi() of previous
   owner reassigned it to us. My fix works. But it looks very stupid.
   I would think about removal of shift of ownership in wake_futex_pi()
   and making all the work in context of process taking lock.

From: Thomas Gleixner 

Fix 1) Avoid the tasklist lock variant of the exit race fix by adding
    an additional state transition to the exit code.

    This fixes also the issue, when a task with recursive segfaults
    is not able to release the futexes.

Fix 2) Cleanup the lookup_pi_state() failure path and solve the -ESRCH
    problem finally.

Fix 3) Solve the fixup_pi_state_owner() problem which needs to do the fixup
    in the lock protected section by using the in_atomic userspace access
    functions.

    This removes also the ugly lock drop / unqueue inside of fixup_pi_state()

Fix 4) Fix a stale lock in the error path of futex_wake_pi()

Added some error checks for verification.

The -EDEADLK problem is solved by the rtmutex fixups.

Cc: Alexey Kuznetsov 
Signed-off-by: Thomas Gleixner 
Acked-by: Ingo Molnar 
Signed-off-by: Chris Wright 
Signed-off-by: Greg Kroah-Hartman

futex: PI state locking fix

2007-03-23T19:49:23+00:00

Testing of -rt by IBM uncovered a locking bug in wake_futex_pi(): the PI
state needs to be locked before we access it.

Signed-off-by: Ingo Molnar 
Acked-by: Thomas Gleixner 
Cc: Chuck Ebbert 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

[PATCH] kernel: change uses of f_{dentry, vfsmnt} to use f_path

2006-12-08T16:28:42+00:00

Change all the uses of f_{dentry,vfsmnt} to f_path.{dentry,mnt} in
linux/kernel/.

Signed-off-by: Josef "Jeff" Sipek 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] struct seq_operations and struct file_operations constification

2006-12-07T16:39:46+00:00

 - move some file_operations structs into the .rodata section

 - move static strings from policy_types[] array into the .rodata section

 - fix generic seq_operations usages, so that those structs may be defined
   as "const" as well

[akpm@osdl.org: couple of fixes]
Signed-off-by: Helge Deller 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] futex: remove unneeded barrier

2006-12-07T16:39:45+00:00

When disassembling a kernel I found around over 90 sync Instructions from
mb, rmb and wmb calls in the kernel and only few of those make any sense to
me.  So here's the first one - I think the wmb() in kernel/futex.c is not
needed on uniprocessors so should become an smb_wmb().

Signed-off-by: Ralf Baechle 
Acked-by: Ingo Molnar 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] futex: init error check

2006-12-07T16:39:41+00:00

Check register_filesystem() and kern_mount() return values.

Cc: Ingo Molnar 
Signed-off-by: Akinobu Mita 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] kernel core: replace kmalloc+memset with kzalloc

2006-12-07T16:39:41+00:00

Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] mm: pagefault_{disable,enable}()

2006-12-07T16:39:21+00:00

Introduce pagefault_{disable,enable}() and use these where previously we did
manual preempt increments/decrements to make the pagefault handler do the
atomic thing.

Currently they still rely on the increased preempt count, but do not rely on
the disabled preemption, this might go away in the future.

(NOTE: the extra barrier() in pagefault_disable might fix some holes on
       machines which have too many registers for their own good)

[heiko.carstens@de.ibm.com: s390 fix]
Signed-off-by: Peter Zijlstra 
Acked-by: Nick Piggin 
Cc: Martin Schwidefsky 
Signed-off-by: Heiko Carstens 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] schedule removal of FUTEX_FD

2006-11-03T20:27:58+00:00

Apparently FUTEX_FD is unfixably racy and nothing uses it (or if it does, it
shouldn't).

Add a warning printk, give any remaining users six months to migrate off it.

Cc: Ulrich Drepper 
Cc: Ingo Molnar 
Acked-by: Thomas Gleixner 
Cc: Rusty Russell 
Cc: Alan Cox 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds