linux-toradex.git/kernel/sched.c, branch v2.6.17.12

cond_resched() fix

2006-08-07T03:52:16+00:00

Fix a bug identified by Zou Nan hai :

If the system is in state SYSTEM_BOOTING, and need_resched() is true,
cond_resched() returns true even though it didn't reschedule.  Consequently
need_resched() remains true and JBD locks up.

Fix that by teaching cond_resched() to only return true if it really did call
schedule().

cond_resched_lock() and cond_resched_softirq() have a problem too.  If we're
in SYSTEM_BOOTING state and need_resched() is true, these functions will drop
the lock and will then try to call schedule(), but the SYSTEM_BOOTING state
will prevent schedule() from being called.  So on return, need_resched() will
still be true, but cond_resched_lock() has to return 1 to tell the caller that
the lock was dropped.  The caller will probably lock up.

Bottom line: if these functions dropped the lock, they _must_ call schedule()
to clear need_resched().   Make it so.

Also, uninline __cond_resched().  It's largeish, and slowpath.

Acked-by: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

Revert "[PATCH] sched: fix interactive task starvation"

2006-05-22T01:54:09+00:00

This reverts commit 5ce74abe788a26698876e66b9c9ce7e7acc25413 (and its
dependent commit 8a5bc075b8d8cf7a87b3f08fad2fba0f5d13295e), because of
audio underruns.

Reported by Rene Herman , who also pinpointed
the exact cause of the underruns:

  "Audio underruns galore, with only ogg123 and firefox (browsing the
   GIT tree online is also a nice trigger by the way).

   If I back it out, everything is fine for me again."

Cc: Rene Herman 
Cc: Mike Galbraith 
Acked-by: Con Kolivas 
Signed-off-by: Linus Torvalds

[PATCH] Remove __devinitdata from notifier block definitions

2006-04-26T15:27:50+00:00

Few of the notifier_chain_register() callers use __devinitdata in the
definition of notifier_block data structure.  It is incorrect as the
data structure should be available after the initializations (they do
not unregister them during initializations).

This was leading to an oops when notifier_chain_register() call is
invoked for those callback chains after initialization.

This patch fixes all such usages to _not_ have the notifier_block data
structure in the init data section.

Signed-off-by: Chandra Seetharaman 
Signed-off-by: Linus Torvalds

[PATCH] sched: don't awaken RT tasks on expired array

2006-04-11T13:18:30+00:00

RT tasks are being awakened on the expired array when expired_starving() is
true, whereas they really should be excluded.  Fix.

Signed-off-by: Mike Galbraith 
Acked-by: Ingo Molnar 
Cc: Con Kolivas 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] sched: fix interactive task starvation

2006-04-11T13:18:30+00:00

Fix a starvation problem that occurs when a stream of highly interactive tasks
delay an array switch for extended periods despite EXPIRED_STARVING(rq) being
true.  AFAIKT, the only choice is to enqueue awakening tasks on the expired
array in this case.

Without this patch, it can be nearly impossible to remotely login to a busy
server, and interactive shell commands can starve for minutes.

Also, convert the EXPIRED_STARVING macro into an inline function which humans
can understand.

Signed-off-by: Mike Galbraith 
Acked-by: Ingo Molnar 
Cc: Nick Piggin 
Acked-by: Con Kolivas 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] sched: activate SCHED BATCH expired

2006-03-31T20:18:59+00:00

To increase the strength of SCHED_BATCH as a scheduling hint we can
activate batch tasks on the expired array since by definition they are
latency insensitive tasks.

Signed-off-by: Con Kolivas 
Acked-by: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] sched: remove on runqueue requeueing

2006-03-31T20:18:59+00:00

On runqueue time is used to elevate priority in schedule().

In the code it currently requeues tasks even if their priority is not
elevated, which would end up placing them at the end of their runqueue
array effectively delaying them instead of improving their priority.

Bug spotted by Mike Galbraith 

This patch removes this requeueing.

Signed-off-by: Con Kolivas 
Acked-by: Ingo Molnar 
Cc: Mike Galbraith 
Cc: Nick Piggin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] sched: include noninteractive sleep in idle detect

2006-03-31T20:18:59+00:00

Tasks waiting in SLEEP_NONINTERACTIVE state can now get to best priority so
they need to be included in the idle detection code.

Signed-off-by: Con Kolivas 
Acked-by: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] sched: dont decrease idle sleep avg

2006-03-31T20:18:58+00:00

We watch for tasks that sleep extended periods and don't allow one single
prolonged sleep period from elevating priority to maximum bonus to prevent cpu
bound tasks from getting high priority with single long sleeps.  There is a
bug in the current code that also penalises tasks that already have high
priority.  Correct that bug.

Signed-off-by: Con Kolivas 
Acked-by: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] sched: make task_noninteractive use sleep_type

2006-03-31T20:18:58+00:00

Alterations to the pipe code in the kernel made it possible for relative
starvation to occur with tasks that slept waiting on a pipe getting unfair
priority bonuses even if they were otherwise fully cpu bound so the
TASK_NONINTERACTIVE flag was introduced which prevented any change to
sleep_avg while sleeping waiting on a pipe.  This change also leads to the
converse though, preventing any priority boost from occurring in truly
interactive tasks that wait on pipes.

Convert the TASK_NONINTERACTIVE flag to set sleep_type to SLEEP_NONINTERACTIVE
which will allow a linear bonus to priority based on sleep time thus allowing
interactive tasks to get high priority if they sleep enough.

Signed-off-by: Con Kolivas 
Acked-by: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds