linux-toradex.git/kernel/hrtimer.c, branch v2.6.25.2

hrtimer: raise softirq unlocked to avoid circular lock dependency

2008-05-01T21:44:39+00:00

commit 0c96c5979a522c3323c30a078a70120e29b5bdbc upstream

The scheduler hrtimer bits in 2.6.25 introduced a circular lock
dependency in a rare code path:

=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.25-sched-devel.git-x86-latest.git #19
-------------------------------------------------------
X/2980 is trying to acquire lock:
 (&rq->rq_lock_key#2){++..}, at: [] task_rq_lock+0x56/0xa0

but task is already holding lock:
 (&cpu_base->lock){++..}, at: [] lock_hrtimer_base+0x31/0x60

which lock already depends on the new lock.

The scenario which leads to this is:

posix-timer signal is delivered
 -> posix-timer is rearmed
    timer is already expired in hrtimer_enqueue()
     -> softirq is raised

To prevent this we need to move the raise of the softirq out of the
base->lock protected code path.

Signed-off-by: Thomas Gleixner 
Acked-by: Peter Zijlstra 
Signed-off-by: Greg Kroah-Hartman

hrtimer: timeout too long when using HRTIMER_CB_SOFTIRQ

2008-05-01T21:44:38+00:00

commit d7b41a24bfb5d7fa02f7b49be1293d468814e424 upstream

When using hrtimer with timer->cb_mode == HRTIMER_CB_SOFTIRQ
in some cases the clockevent is not programmed.
This happens, if:
 - a timer is rearmed while it's state is HRTIMER_STATE_CALLBACK
 - hrtimer_reprogram() returns -ETIME, when it is called after
   CALLBACK is finished. This occurs if the new timer->expires
   is in the past when CALLBACK is done.
In this case, the timer needs to be removed from the tree and put
onto the pending list again.

The patch is against 2.6.22.5, but AFAICS, it is relevant
for 2.6.25 also (in run_hrtimer_pending()).

Signed-off-by: Bodo Stroesser 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

hrtimer: catch expired CLOCK_REALTIME timers early

2008-02-14T21:08:30+00:00

A CLOCK_REALTIME timer, which has an absolute expiry time less than
the clock realtime offset calls with a negative delta into the clock
events code and triggers the WARN_ON() there.

This is a false positive and needs to be prevented. Check the result
of timer->expires - timer->base->offset right away and return -ETIME
right away.

Thanks to Frans Pop, who reported the problem and tested the fixes.

Signed-off-by: Thomas Gleixner 
Tested-by: Frans Pop

hrtimer: check relative timeouts for overflow

2008-02-14T21:08:30+00:00

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

hrtimer: don't modify restart_block->fn in restart functions

2008-02-10T09:48:03+00:00

hrtimer_nanosleep_restart() clears/restores restart_block->fn. This is
pointless and complicates its usage. Note that if sys_restart_syscall()
doesn't actually happen, we have a bogus "pending" restart->fn anyway,
this is harmless.

Signed-off-by: Oleg Nesterov 
Cc: Alexey Dobriyan 
Cc: Pavel Emelyanov 
Cc: Peter Zijlstra 
Cc: Toyo Abe 
Cc: Andrew Morton 
Signed-off-by: Thomas Gleixner

hrtimer: fix *rmtp handling in hrtimer_nanosleep()

2008-02-10T09:48:03+00:00

Spotted by Pavel Emelyanov and Alexey Dobriyan.

hrtimer_nanosleep() sets restart_block->arg1 = rmtp, but this rmtp points to
the local variable which lives in the caller's stack frame. This means that
if sys_restart_syscall() actually happens and it is interrupted as well, we
don't update the user-space variable, but write into the already dead stack
frame.

Introduced by commit 04c227140fed77587432667a574b14736a06dd7f
hrtimer: Rework hrtimer_nanosleep to make sys_compat_nanosleep easier

Change the callers to pass "__user *rmtp" to hrtimer_nanosleep(), and change
hrtimer_nanosleep() to use copy_to_user() to actually update *rmtp.

Small problem remains. man 2 nanosleep states that *rtmp should be written if
nanosleep() was interrupted (it says nothing whether it is OK to update *rmtp
if nanosleep returns 0), but (with or without this patch) we can dirty *rem
even if nanosleep() returns 0.

NOTE: this patch doesn't change compat_sys_nanosleep(), because it has other
bugs. Fixed by the next patch.

Signed-off-by: Oleg Nesterov 
Cc: Alexey Dobriyan 
Cc: Michael Kerrisk 
Cc: Pavel Emelyanov 
Cc: Peter Zijlstra 
Cc: Toyo Abe 
Cc: Andrew Morton 
Signed-off-by: Thomas Gleixner 

 include/linux/hrtimer.h |    2 -
 kernel/hrtimer.c        |   51 +++++++++++++++++++++++++-----------------------
 kernel/posix-timers.c   |   14 +------------
 3 files changed, 30 insertions(+), 37 deletions(-)

timerfd: new timerfd API

2008-02-05T17:44:07+00:00

This is the new timerfd API as it is implemented by the following patch:

int timerfd_create(int clockid, int flags);
int timerfd_settime(int ufd, int flags,
		    const struct itimerspec *utmr,
		    struct itimerspec *otmr);
int timerfd_gettime(int ufd, struct itimerspec *otmr);

The timerfd_create() API creates an un-programmed timerfd fd.  The "clockid"
parameter can be either CLOCK_MONOTONIC or CLOCK_REALTIME.

The timerfd_settime() API give new settings by the timerfd fd, by optionally
retrieving the previous expiration time (in case the "otmr" parameter is not
NULL).

The time value specified in "utmr" is absolute, if the TFD_TIMER_ABSTIME bit
is set in the "flags" parameter.  Otherwise it's a relative time.

The timerfd_gettime() API returns the next expiration time of the timer, or
{0, 0} if the timerfd has not been set yet.

Like the previous timerfd API implementation, read(2) and poll(2) are
supported (with the same interface).  Here's a simple test program I used to
exercise the new timerfd APIs:

http://www.xmailserver.org/timerfd-test2.c

[akpm@linux-foundation.org: coding-style cleanups]
[akpm@linux-foundation.org: fix ia64 build]
[akpm@linux-foundation.org: fix m68k build]
[akpm@linux-foundation.org: fix mips build]
[akpm@linux-foundation.org: fix alpha, arm, blackfin, cris, m68k, s390, sparc and sparc64 builds]
[heiko.carstens@de.ibm.com: fix s390]
[akpm@linux-foundation.org: fix powerpc build]
[akpm@linux-foundation.org: fix sparc64 more]
Signed-off-by: Davide Libenzi 
Cc: Michael Kerrisk 
Cc: Thomas Gleixner 
Cc: Davide Libenzi 
Cc: Michael Kerrisk 
Cc: Martin Schwidefsky 
Signed-off-by: Heiko Carstens 
Cc: Michael Kerrisk 
Cc: Davide Libenzi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

hrtimer: fix hrtimer_init_sleeper() users

2008-02-01T16:45:13+00:00

this patch:

 commit 37bb6cb4097e29ffee970065b74499cbf10603a3
 Author: Peter Zijlstra 
 Date:   Fri Jan 25 21:08:32 2008 +0100

     hrtimer: unlock hrtimer_wakeup

Broke hrtimer_init_sleeper() users. It forgot to fix up the futex
caller of this function to detect the failed queueing and messed up
the do_nanosleep() caller in that it could leak a TASK_INTERRUPTIBLE
state.

Signed-off-by: Peter Zijlstra 
Signed-off-by: Ingo Molnar

hrtimer: unlock hrtimer_wakeup

2008-01-25T20:08:32+00:00

hrtimer_wakeup creates a

  base->lock
    rq->lock

lock dependancy. Avoid this by switching to HRTIMER_CB_IRQSAFE_NO_SOFTIRQ
which doesn't hold base->lock.

This fully untangles hrtimer locks from the scheduler locks, and allows
hrtimer usage in the scheduler proper.

Signed-off-by: Peter Zijlstra 
Signed-off-by: Ingo Molnar

hrtimer: fixup the HRTIMER_CB_IRQSAFE_NO_SOFTIRQ fallback

2008-01-25T20:08:31+00:00

Currently all highres=off timers are run from softirq context, but
HRTIMER_CB_IRQSAFE_NO_SOFTIRQ timers expect to run from irq context.

Fix this up by splitting it similar to the highres=on case.

Signed-off-by: Peter Zijlstra 
Signed-off-by: Ingo Molnar