linux-toradex.git/arch/s390, branch v2.6.36.4

nmi: fix clock comparator revalidation

2010-12-09T21:33:35+00:00

commit e8129c642155616d9e2160a75f103e127c8c3708 upstream.

On each machine check all registers are revalidated. The save area for
the clock comparator however only contains the upper most seven bytes
of the former contents, if valid.
Therefore the machine check handler uses a store clock instruction to
get the current time and writes that to the clock comparator register
which in turn will generate an immediate timer interrupt.
However within the lowcore the expected time of the next timer
interrupt is stored. If the interrupt happens before that time the
handler won't be called. In turn the clock comparator won't be
reprogrammed and therefore the interrupt condition stays pending which
causes an interrupt loop until the expected time is reached.

On NOHZ machines this can result in unresponsive machines since the
time of the next expected interrupted can be a couple of days in the
future.

To fix this just revalidate the clock comparator register with the
expected value.
In addition the special handling for udelay must be changed as well.

Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky 
Signed-off-by: Greg Kroah-Hartman

nohz/s390: fix arch_needs_cpu() return value on offline cpus

2010-12-09T21:33:27+00:00

commit 398812159e328478ae49b4bd01f0d71efea96c39 upstream.

This fixes the same problem as described in the patch "nohz: fix
printk_needs_cpu() return value on offline cpus" for the arch_needs_cpu()
primitive:

arch_needs_cpu() may return 1 if called on offline cpus. When a cpu gets
offlined it schedules the idle process which, before killing its own cpu,
will call tick_nohz_stop_sched_tick().
That function in turn will call arch_needs_cpu() in order to check if the
local tick can be disabled. On offline cpus this function should naturally
return 0 since regardless if the tick gets disabled or not the cpu will be
dead short after. That is besides the fact that __cpu_disable() should already
have made sure that no interrupts on the offlined cpu will be delivered anyway.

In this case it prevents tick_nohz_stop_sched_tick() to call
select_nohz_load_balancer(). No idea if that really is a problem. However what
made me debug this is that on 2.6.32 the function get_nohz_load_balancer() is
used within __mod_timer() to select a cpu on which a timer gets enqueued.
If arch_needs_cpu() returns 1 then the nohz_load_balancer cpu doesn't get
updated when a cpu gets offlined. It may contain the cpu number of an offline
cpu. In turn timers get enqueued on an offline cpu and not very surprisingly
they never expire and cause system hangs.

This has been observed 2.6.32 kernels. On current kernels __mod_timer() uses
get_nohz_timer_target() which doesn't have that problem. However there might
be other problems because of the too early exit tick_nohz_stop_sched_tick()
in case a cpu goes offline.

This specific bug was indrocuded with 3c5d92a0 "nohz: Introduce
arch_needs_cpu".

In this case a cpu hotplug notifier is used to fix the issue in order to keep
the normal/fast path small. All we need to do is to clear the condition that
makes arch_needs_cpu() return 1 since it is just a performance improvement
which is supposed to keep the local tick running for a short period if a cpu
goes idle. Nothing special needs to be done except for clearing the condition.

Acked-by: Peter Zijlstra 
Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky 
Signed-off-by: Greg Kroah-Hartman

modules: Fix module_bug_list list corruption race

2010-10-05T18:29:27+00:00

With all the recent module loading cleanups, we've minimized the code
that sits under module_mutex, fixing various deadlocks and making it
possible to do most of the module loading in parallel.

However, that whole conversion totally missed the rather obscure code
that adds a new module to the list for BUG() handling.  That code was
doubly obscure because (a) the code itself lives in lib/bugs.c (for
dubious reasons) and (b) it gets called from the architecture-specific
"module_finalize()" rather than from generic code.

Calling it from arch-specific code makes no sense what-so-ever to begin
with, and is now actively wrong since that code isn't protected by the
module loading lock any more.

So this commit moves the "module_bug_{finalize,cleanup}()" calls away
from the arch-specific code, and into the generic code - and in the
process protects it with the module_mutex so that the list operations
are now safe.

Future fixups:
 - move the module list handling code into kernel/module.c where it
   belongs.
 - get rid of 'module_bug_list' and just use the regular list of modules
   (called 'modules' - imagine that) that we already create and maintain
   for other reasons.

Reported-and-tested-by: Thomas Gleixner 
Cc: Rusty Russell 
Cc: Adrian Bunk 
Cc: Andrew Morton 
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds

compat: Make compat_alloc_user_space() incorporate the access_ok()

2010-09-14T23:08:45+00:00

compat_alloc_user_space() expects the caller to independently call
access_ok() to verify the returned area.  A missing call could
introduce problems on some architectures.

This patch incorporates the access_ok() check into
compat_alloc_user_space() and also adds a sanity check on the length.
The existing compat_alloc_user_space() implementations are renamed
arch_compat_alloc_user_space() and are used as part of the
implementation of the new global function.

This patch assumes NULL will cause __get_user()/__put_user() to either
fail or access userspace on all architectures.  This should be
followed by checking the return value of compat_access_user_space()
for NULL in the callers, at which time the access_ok() in the callers
can also be removed.

Reported-by: Ben Hawkes 
Signed-off-by: H. Peter Anvin 
Acked-by: Benjamin Herrenschmidt 
Acked-by: Chris Metcalf 
Acked-by: David S. Miller 
Acked-by: Ingo Molnar 
Acked-by: Thomas Gleixner 
Acked-by: Tony Luck 
Cc: Andrew Morton 
Cc: Arnd Bergmann 
Cc: Fenghua Yu 
Cc: H. Peter Anvin 
Cc: Heiko Carstens 
Cc: Helge Deller 
Cc: James Bottomley 
Cc: Kyle McMartin 
Cc: Martin Schwidefsky 
Cc: Paul Mackerras 
Cc: Ralf Baechle 
Cc:

[S390] fix tlb flushing vs. concurrent /proc accesses

2010-08-24T07:26:34+00:00

The tlb flushing code uses the mm_users field of the mm_struct to
decide if each page table entry needs to be flushed individually with
IPTE or if a global flush for the mm_struct is sufficient after all page
table updates have been done. The comment for mm_users says "How many
users with user space?" but the /proc code increases mm_users after it
found the process structure by pid without creating a new user process.
Which makes mm_users useless for the decision between the two tlb
flusing methods. The current code can be confused to not flush tlb
entries by a concurrent access to /proc files if e.g. a fork is in
progres. The solution for this problem is to make the tlb flushing
logic independent from the mm_users field.

Signed-off-by: Martin Schwidefsky

[S390] s390: fix build error (sys_execve)

2010-08-24T07:26:34+00:00

fix this build error:
arch/s390/kernel/process.c:272: error: conflicting types for 'sys_execve'
arch/s390/kernel/entry.h:45: error: previous declaration of 'sys_execve' was here
make[1]: *** [arch/s390/kernel/process.o] Error 1
make: *** [arch/s390/kernel] Error 2

introduced by d7627467b7a8dd6944885290a03a07ceb28c10eb

Signed-off-by: Sebastian Ott 
Signed-off-by: Martin Schwidefsky

Make do_execve() take a const filename pointer

2010-08-18T01:07:43+00:00

Make do_execve() take a const filename pointer so that kernel_execve() compiles
correctly on ARM:

arch/arm/kernel/sys_arm.c:88: warning: passing argument 1 of 'do_execve' discards qualifiers from pointer target type

This also requires the argv and envp arguments to be consted twice, once for
the pointer array and once for the strings the array points to.  This is
because do_execve() passes a pointer to the filename (now const) to
copy_strings_kernel().  A simpler alternative would be to cast the filename
pointer in do_execve() when it's passed to copy_strings_kernel().

do_execve() may not change any of the strings it is passed as part of the argv
or envp lists as they are some of them in .rodata, so marking these strings as
const should be fine.

Further kernel_execve() and sys_execve() need to be changed to match.

This has been test built on x86_64, frv, arm and mips.

Signed-off-by: David Howells 
Tested-by: Ralf Baechle 
Acked-by: Russell King 
Signed-off-by: Linus Torvalds

defconfig reduction

2010-08-14T20:26:53+00:00

Use the defconfig files generated by "make savedefconfig" for
remaining defconfig files.

Signed-off-by: Sam Ravnborg

archs: replace unifdef-y with header-y

2010-08-14T20:26:51+00:00

unifdef-y and header-y have same semantic, so drop unifdef-y

Signed-off-by: Sam Ravnborg

Mark arguments to certain syscalls as being const

2010-08-13T23:53:13+00:00

Mark arguments to certain system calls as being const where they should be but
aren't.  The list includes:

 (*) The filename arguments of various stat syscalls, execve(), various utimes
     syscalls and some mount syscalls.

 (*) The filename arguments of some syscall helpers relating to the above.

 (*) The buffer argument of various write syscalls.

Signed-off-by: David Howells 
Acked-by: David S. Miller 
Signed-off-by: Linus Torvalds