linux-toradex.git/kernel/up.c, branch v4.8-rc6

smp: Rename __smp_call_function_single() to smp_call_function_single_async()

2014-02-24T22:47:15+00:00

The name __smp_call_function_single() doesn't tell much about the
properties of this function, especially when compared to
smp_call_function_single().

The comments above the implementation are also misleading. The main
point of this function is actually not to be able to embed the csd
in an object. This is actually a requirement that result from the
purpose of this function which is to raise an IPI asynchronously.

As such it can be called with interrupts disabled. And this feature
comes at the cost of the caller who then needs to serialize the
IPIs on this csd.

Lets rename the function and enhance the comments so that they reflect
these properties.

Suggested-by: Christoph Hellwig 
Cc: Andrew Morton 
Cc: Christoph Hellwig 
Cc: Ingo Molnar 
Cc: Jan Kara 
Cc: Jens Axboe 
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Jens Axboe

smp: Remove wait argument from __smp_call_function_single()

2014-02-24T22:47:09+00:00

The main point of calling __smp_call_function_single() is to send
an IPI in a pure asynchronous way. By embedding a csd in an object,
a caller can send the IPI without waiting for a previous one to complete
as is required by smp_call_function_single() for example. As such,
sending this kind of IPI can be safe even when irqs are disabled.

This flexibility comes at the expense of the caller who then needs to
synchronize the csd lifecycle by himself and make sure that IPIs on a
single csd are serialized.

This is how __smp_call_function_single() works when wait = 0 and this
usecase is relevant.

Now there don't seem to be any usecase with wait = 1 that can't be
covered by smp_call_function_single() instead, which is safer. Lets look
at the two possible scenario:

1) The user calls __smp_call_function_single(wait = 1) on a csd embedded
   in an object. It looks like a nice and convenient pattern at the first
   sight because we can then retrieve the object from the IPI handler easily.

   But actually it is a waste of memory space in the object since the csd
   can be allocated from the stack by smp_call_function_single(wait = 1)
   and the object can be passed an the IPI argument.

   Besides that, embedding the csd in an object is more error prone
   because the caller must take care of the serialization of the IPIs
   for this csd.

2) The user calls __smp_call_function_single(wait = 1) on a csd that
   is allocated on the stack. It's ok but smp_call_function_single()
   can do it as well and it already takes care of the allocation on the
   stack. Again it's more simple and less error prone.

Therefore, using the underscore prepend API version with wait = 1
is a bad pattern and a sign that the caller can do safer and more
simple.

There was a single user of that which has just been converted.
So lets remove this option to discourage further users.

Cc: Andrew Morton 
Cc: Christoph Hellwig 
Cc: Ingo Molnar 
Cc: Jan Kara 
Cc: Jens Axboe 
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Jens Axboe

smp: Teach __smp_call_function_single() to check for offline cpus

2014-02-24T22:46:55+00:00

Align __smp_call_function_single() with smp_call_function_single() so
that it also checks whether requested cpu is still online.

Signed-off-by: Jan Kara 
Cc: Andrew Morton 
Cc: Christoph Hellwig 
Cc: Ingo Molnar 
Cc: Jens Axboe 
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Jens Axboe

kernel: provide a __smp_call_function_single stub for !CONFIG_SMP

2013-11-15T00:32:22+00:00

Signed-off-by: Christoph Hellwig 
Cc: Jan Kara 
Cc: Jens Axboe 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

smp.h: move !SMP version of on_each_cpu() out-of-line

2013-09-11T22:58:25+00:00

All of the other non-trivial !SMP versions of functions in smp.h are
out-of-line in up.c.  Move on_each_cpu() there as well.

This allows us to get rid of the #include .  The
drawback is that this makes both the x86_64 and i386 defconfig !SMP
kernels about 200 bytes larger each.

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

up.c: use local_irq_{save,restore}() in smp_call_function_single.

2013-09-11T22:58:25+00:00

The SMP version of this function doesn't unconditionally enable irqs, so
neither should this !SMP version.  There are no know problems caused by
this, but we make the change for consistency's sake.

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

smp: quit unconditionally enabling irq in on_each_cpu_mask and on_each_cpu_cond

2013-09-11T22:58:23+00:00

As in commit f21afc25f9ed ("smp.h: Use local_irq_{save,restore}() in
!SMP version of on_each_cpu()"), we don't want to enable irqs if they
are not already enabled.  There are currently no known problematical
callers of these functions, but since it is a known failure pattern, we
preemptively fix them.

Since they are not trivial functions, make them non-inline by moving
them to up.c.  This also makes it so we don't have to fix #include
dependancies for preempt_{disable,enable}.

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

kernel: Map most files to use export.h instead of module.h

2011-10-31T13:20:12+00:00

The changed files were only including linux/module.h for the
EXPORT_SYMBOL infrastructure, and nothing else.  Revector them
onto the isolated export header for faster compile times.

Nothing to see here but a whole lot of instances of:

  -#include 
  +#include 

This commit is only changing the kernel dir; next targets
will probably be mm, fs, the arch dirs, etc.

Signed-off-by: Paul Gortmaker

smp_call_function_single(): be slightly less stupid, fix #2

2009-01-12T15:04:37+00:00

fix m68k build failure:

 tip/kernel/up.c: In function 'smp_call_function_single':
 tip/kernel/up.c:16: error: dereferencing pointer to incomplete type
 make[2]: *** [kernel/up.o] Error 1

Signed-off-by: Ingo Molnar

smp_call_function_single(): be slightly less stupid, fix

2009-01-11T04:15:21+00:00

Impact: build fix on Alpha

 kernel/up.c: In function 'smp_call_function_single':
 kernel/up.c:12: error: 'cpuid' undeclared (first use in this function)
 kernel/up.c:12: error: (Each undeclared identifier is reported only once
 kernel/up.c:12: error: for each function it appears in.)

The typo didnt show up on x86 because 'cpuid' happens to be a
function address as well ...

Signed-off-by: Ingo Molnar