linux-toradex.git/kernel/stop_machine.c, branch v2.6.29-rc1

stop_machine: introduce stop_machine_create/destroy.

2009-01-04T22:10:14+00:00

Introduce stop_machine_create/destroy. With this interface subsystems
that need a non-failing stop_machine environment can create the
stop_machine machine threads before actually calling stop_machine.
When the threads aren't needed anymore they can be killed with
stop_machine_destroy again.

When stop_machine gets called and the threads aren't present they
will be created and destroyed automatically. This restores the old
behaviour of stop_machine.

This patch also converts cpu hotplug to the new interface since it
is special: cpu_down calls __stop_machine instead of stop_machine.
However the kstop threads will only be created when stop_machine
gets called.

Changing the code so that the threads would be created automatically
on __stop_machine is currently not possible: when __stop_machine gets
called we hold cpu_add_remove_lock, which is the same lock that
create_rt_workqueue would take. So the workqueue needs to be created
before the cpu hotplug code locks cpu_add_remove_lock.

Signed-off-by: Heiko Carstens 
Signed-off-by: Rusty Russell

cpumask: convert rest of files in kernel/

2008-12-31T23:42:28+00:00

Impact: Reduce stack usage, use new cpumask API.

Mainly changing cpumask_t to 'struct cpumask' and similar simple API
conversion.  Two conversions worth mentioning:

1) we use cpumask_any_but to avoid a temporary in kernel/softlockup.c,
2) Use cpumask_var_t in taskstats_user_cmd().

Signed-off-by: Rusty Russell 
Signed-off-by: Mike Travis 
Cc: Balbir Singh 
Cc: Ingo Molnar

stop_machine: fix race with return value (fixes Bug #11989)

2008-11-16T23:09:52+00:00

Bug #11989: Suspend failure on NForce4-based boards due to chanes in
stop_machine

We should not access active.fnret outside the lock; in theory the next
stop_machine could overwrite it.

Signed-off-by: Rusty Russell 
Tested-by: "Rafael J. Wysocki" 
Signed-off-by: Linus Torvalds

Revert "Call init_workqueues before pre smp initcalls."

2008-10-26T02:53:38+00:00

This reverts commit a802dd0eb5fc97a50cf1abb1f788a8f6cc5db635 by moving
the call to init_workqueues() back where it belongs - after SMP has been
initialized.

It also moves stop_machine_init() - which needs workqueues - to a later
phase using a core_initcall() instead of early_initcall().  That should
satisfy all ordering requirements, and was apparently the reason why
init_workqueues() was moved to be too early.

Cc: Heiko Carstens 
Cc: Rusty Russell 
Signed-off-by: Linus Torvalds

stop_machine: fix error code handling on multiple cpus

2008-10-21T23:00:26+00:00

Using |= for updating a value which might be updated on several cpus
concurrently will not always work since we need to make sure that the
update happens atomically.
To fix this just use a write if the called function returns an error
code on a cpu. We end up writing the error code of an arbitrary cpu
if multiple ones fail but that should be sufficient.

Signed-off-by: Heiko Carstens 
Signed-off-by: Rusty Russell

stop_machine: use workqueues instead of kernel threads

2008-10-21T23:00:26+00:00

Convert stop_machine to a workqueue based approach. Instead of using kernel
threads for stop_machine we now use a an rt workqueue to synchronize all
cpus.
This has the advantage that all needed per cpu threads are already created
when stop_machine gets called. And therefore a call to stop_machine won't
fail anymore. This is needed for s390 which needs a mechanism to synchronize
all cpus without allocating any memory.
As Rusty pointed out free_module() needs a non-failing stop_machine interface
as well.

As a side effect the stop_machine code gets simplified.

Signed-off-by: Heiko Carstens 
Signed-off-by: Rusty Russell

stop_machine: remove unused variable

2008-08-12T07:52:55+00:00

Signed-off-by: Li Zefan 
Signed-off-by: Rusty Russell

stop_machine(): stop_machine_run() changed to use cpu mask

2008-07-28T02:16:30+00:00

Instead of a "cpu" arg with magic values NR_CPUS (any cpu) and ~0 (all
cpus), pass a cpumask_t.  Allow NULL for the common case (where we
don't care which CPU the function is run on): temporary cpumask_t's
are usually considered bad for stack space.

This deprecates stop_machine_run, to be removed soon when all the
callers are dead.

Signed-off-by: Rusty Russell

Simplify stop_machine

2008-07-28T02:16:29+00:00

stop_machine creates a kthread which creates kernel threads.  We can
create those threads directly and simplify things a little.  Some care
must be taken with CPU hotunplug, which has special needs, but that code
seems more robust than it was in the past.

Signed-off-by: Rusty Russell 
Acked-by: Christian Borntraeger

stop_machine: add ALL_CPUS option

2008-07-28T02:16:28+00:00

-allow stop_mahcine_run() to call a function on all cpus. Calling
 stop_machine_run() with a 'ALL_CPUS' invokes this new behavior.
 stop_machine_run() proceeds as normal until the calling cpu has
 invoked 'fn'. Then, we tell all the other cpus to call 'fn'.

Signed-off-by: Jason Baron 
Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Rusty Russell 
CC: Adrian Bunk 
CC: Andi Kleen 
CC: Alexey Dobriyan 
CC: Christoph Hellwig 
CC: mingo@elte.hu
CC: akpm@osdl.org