linux/kernel/futex.c, branch v2.6.28

hrtimer: make the futex() system call use the per process slack value

2008-09-11T14:17:00Z

This patch makes the futex() system call use the per process slack value; with this users are able to externally control existing applications to reduce the wakeup rate. Signed-off-by: Arjan van de Ven

hrtimer: convert kernel/* to the new hrtimer apis

2008-09-06T04:35:13Z

In order to be able to do range hrtimers we need to use accessor functions to the "expire" member of the hrtimer struct. This patch converts kernel/* to these accessors. Signed-off-by: Arjan van de Ven

futexes: fix fault handling in futex_lock_pi

2008-06-23T11:31:15Z

This patch addresses a very sporadic pi-futex related failure in highly threaded java apps on large SMP systems. David Holmes reported that the pi_state consistency check in lookup_pi_state triggered with his test application. This means that the kernel internal pi_state and the user space futex variable are out of sync. First we assumed that this is a user space data corruption, but deeper investigation revieled that the problem happend because the pi-futex code is not handling a fault in the futex_lock_pi path when the user space variable needs to be fixed up. The fault happens when a fork mapped the anon memory which contains the futex readonly for COW or the page got swapped out exactly between the unlock of the futex and the return of either the new futex owner or the task which was the expected owner but failed to acquire the kernel internal rtmutex. The current futex_lock_pi() code drops out with an inconsistent in case it faults and returns -EFAULT to user space. User space has no way to fixup that state. When we wrote this code we thought that we could not drop the hash bucket lock at this point to handle the fault. After analysing the code again it turned out to be wrong because there are only two tasks involved which might modify the pi_state and the user space variable: - the task which acquired the rtmutex - the pending owner of the pi_state which did not get the rtmutex Both tasks drop into the fixup_pi_state() function before returning to user space. The first task which acquired the hash bucket lock faults in the fixup of the user space variable, drops the spinlock and calls futex_handle_fault() to fault in the page. Now the second task could acquire the hash bucket lock and tries to fixup the user space variable as well. It either faults as well or it succeeds because the first task already faulted the page in. One caveat is to avoid a double fixup. After returning from the fault handling we reacquire the hash bucket lock and check whether the pi_state owner has been modified already. Reported-by: David Holmes Signed-off-by: Thomas Gleixner Cc: Andrew Morton Cc: David Holmes Cc: Peter Zijlstra Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Signed-off-by: Ingo Molnar kernel/futex.c | 93 ++++++++++++++++++++++++++++++++++++++++++++------------- 1 file changed, 73 insertions(+), 20 deletions(-)

Removal of FUTEX_FD

2008-05-05T15:18:45Z

Since FUTEX_FD was scheduled for removal in June 2007 lets remove it. Google Code search found no users for it and NGPT was abandoned in 2003 according to IBM. futex.h is left untouched to make sure the id does not get reassigned. Since queue_me() has no users left it is commented out to avoid a warning, i didnt remove it completely since it is part of the internal api (matching unqueue_me()) Signed-off-by: Eric Sesterhenn Signed-off-by: Rusty Russell (removed rest) Acked-by: Thomas Gleixner Signed-off-by: Linus Torvalds

add hrtimer specific debugobjects code

2008-04-30T15:29:53Z

hrtimers have now dynamic users in the network code. Put them under debugobjects surveillance as well. Add calls to the generic object debugging infrastructure and provide fixup functions which allow to keep the system alive when recoverable problems have been detected by the object debugging core code. Signed-off-by: Thomas Gleixner Cc: Greg KH Cc: Randy Dunlap Cc: Kay Sievers Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

NULL noise: fs/, mm/, kernel/*

2008-03-30T21:18:41Z

Signed-off-by: Al Viro Signed-off-by: Linus Torvalds

Give futex init a proper name

2008-03-27T15:02:13Z

The futex init function is called init(). This is a pain in the neck when debugging when you code dies in ... init :-) This renames it to futex_init(). Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Linus Torvalds

futex: runtime enable pi and robust functionality

2008-02-24T01:12:15Z

Not all architectures implement futex_atomic_cmpxchg_inatomic(). The default implementation returns -ENOSYS, which is currently not handled inside of the futex guts. Futex PI calls and robust list exits with a held futex result in an endless loop in the futex code on architectures which have no support. Fixing up every place where futex_atomic_cmpxchg_inatomic() is called would add a fair amount of extra if/else constructs to the already complex code. It is also not possible to disable the robust feature before user space tries to register robust lists. Compile time disabling is not a good idea either, as there are already architectures with runtime detection of futex_atomic_cmpxchg_inatomic support. Detect the functionality at runtime instead by calling cmpxchg_futex_value_locked() with a NULL pointer from the futex initialization code. This is guaranteed to fail, but the call of futex_atomic_cmpxchg_inatomic() happens with pagefaults disabled. On architectures, which use the asm-generic implementation or have a runtime CPU feature detection, a -ENOSYS return value disables the PI/robust features. On architectures with a working implementation the call returns -EFAULT and the PI/robust features are enabled. The relevant syscalls return -ENOSYS and the robust list exit code is blocked, when the detection fails. Fixes http://lkml.org/lkml/2008/2/11/149 Originally reported by: Lennart Buytenhek Signed-off-by: Thomas Gleixner Acked-by: Ingo Molnar Cc: Lennert Buytenhek Cc: Riku Voipio Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

futex: fix init order

2008-02-24T01:12:15Z

When the futex init code fails to initialize the futex pseudo file system it returns early without initializing the hash queues. Should the boot succeed then a futex syscall which tries to enqueue a waiter on the hashqueue will crash due to the unitilialized plist heads. Initialize the hash queues before the filesystem. Signed-off-by: Thomas Gleixner Acked-by: Ingo Molnar Cc: Lennert Buytenhek Cc: Riku Voipio Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

hrtimer: check relative timeouts for overflow

2008-02-14T21:08:30Z

Various user space callers ask for relative timeouts. While we fixed that overflow issue in hrtimer_start(), the sites which convert relative user space values to absolute timeouts themself were uncovered. Instead of putting overflow checks into each place add a function which does the sanity checking and convert all affected callers to use it. Thanks to Frans Pop, who reported the problem and tested the fixes. Signed-off-by: Thomas Gleixner Acked-by: Ingo Molnar Tested-by: Frans Pop

linux/kernel/futex.c, branch v2.6.28

hrtimer: make the futex() system call use the per process slack value

hrtimer: convert kernel/* to the new hrtimer apis

futexes: fix fault handling in futex_lock_pi

Removal of FUTEX_FD

add hrtimer specific debugobjects code

NULL noise: fs/*, mm/*, kernel/*

Give futex init a proper name

futex: runtime enable pi and robust functionality

futex: fix init order

hrtimer: check relative timeouts for overflow

NULL noise: fs/, mm/, kernel/*