linux-toradex.git/arch/s390, branch v3.2.26

s390/idle: fix sequence handling vs cpu hotplug

2012-08-02T13:37:50+00:00

commit 0008204ffe85d23382d6fd0f971f3f0fbe70bae2 upstream.

The s390 idle accounting code uses a sequence counter which gets used
when the per cpu idle statistics get updated and read.

One assumption on read access is that only when the sequence counter is
even and did not change while reading all values the result is valid.
On cpu hotplug however the per cpu data structure gets initialized via
a cpu hotplug notifier on CPU_ONLINE.
CPU_ONLINE however is too late, since the onlined cpu is already running
and might access the per cpu data. Worst case is that the data structure
gets initialized while an idle thread is updating its idle statistics.
This will result in an uneven sequence counter after an update.

As a result user space tools like top, which access /proc/stat in order
to get idle stats, will busy loop waiting for the sequence counter to
become even again, which will never happen until the queried cpu will
update its idle statistics again. And even then the sequence counter
will only have an even value for a couple of cpu cycles.

Fix this by moving the initialization of the per cpu idle statistics
to cpu_init(). I prefer that solution in favor of changing the
notifier to CPU_UP_PREPARE, which would be a different solution to
the problem.

Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky 
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings

s390/pfault: fix task state race

2012-05-30T23:43:28+00:00

commit d5e50a51ccbda36b379aba9d1131a852eb908dda upstream.

When setting the current task state to TASK_UNINTERRUPTIBLE this can
race with a different cpu. The other cpu could set the task state after
it inspected it (while it was still TASK_RUNNING) to TASK_RUNNING which
would change the state from TASK_UNINTERRUPTIBLE to TASK_RUNNING again.

This race was always present in the pfault interrupt code but didn't
cause anything harmful before commit f2db2e6c "[S390] pfault: cpu hotplug
vs missing completion interrupts" which relied on the fact that after
setting the task state to TASK_UNINTERRUPTIBLE the task would really
sleep.
Since this is not necessarily the case the result may be a list corruption
of the pfault_list or, as observed, a use-after-free bug while trying to
access the task_struct of a task which terminated itself already.

To fix this, we need to get a reference of the affected task when receiving
the initial pfault interrupt and add special handling if we receive yet
another initial pfault interrupt when the task is already enqueued in the
pfault list.

Signed-off-by: Heiko Carstens 
Reviewed-by: Martin Schwidefsky 
Signed-off-by: Martin Schwidefsky 
Signed-off-by: Ben Hutchings

KVM: s390: Sanitize fpc registers for KVM_SET_FPU

2012-05-30T23:43:14+00:00

(cherry picked from commit 851755871c1f3184f4124c466e85881f17fa3226)

commit 7eef87dc99e419b1cc051e4417c37e4744d7b661 (KVM: s390: fix
register setting) added a load of the floating point control register
to the KVM_SET_FPU path. Lets make sure that the fpc is valid.

Signed-off-by: Christian Borntraeger 
Signed-off-by: Marcelo Tosatti 
Signed-off-by: Avi Kivity 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Ben Hutchings

KVM: s390: do store status after handling STOP_ON_STOP bit

2012-05-30T23:43:13+00:00

(cherry picked from commit 9e0d5473e2f0ba2d2fe9dab9408edef3060b710e)

In handle_stop() handle the stop bit before doing the store status as
described for "Stop and Store Status" in the Principles of Operation.
We have to give up the local_int.lock before calling kvm store status
since it calls gmap_fault() which might sleep. Since local_int.lock
only protects local_int.* and not guest memory we can give up the lock.

Signed-off-by: Jens Freimann 
Signed-off-by: Christian Borntraeger 
Signed-off-by: Marcelo Tosatti 
Signed-off-by: Avi Kivity 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Ben Hutchings

fix tlb flushing for page table pages

2012-04-22T22:31:10+00:00

commit cd94154cc6a28dd9dc271042c1a59c08d26da886 upstream.

Git commit 36409f6353fc2d7b6516e631415f938eadd92ffa "use generic RCU
page-table freeing code" introduced a tlb flushing bug. Partially revert
the above git commit and go back to s390 specific page table flush code.

For s390 the TLB can contain three types of entries, "normal" TLB
page-table entries, TLB combined region-and-segment-table (CRST) entries
and real-space entries. Linux does not use real-space entries which
leaves normal TLB entries and CRST entries. The CRST entries are
intermediate steps in the page-table translation called translation paths.
For example a 4K page access in a three-level page table setup will
create two CRST TLB entries and one page-table TLB entry. The advantage
of that approach is that a page access next to the previous one can reuse
the CRST entries and needs just a single read from memory to create the
page-table TLB entry. The disadvantage is that the TLB flushing rules are
more complicated, before any page-table may be freed the TLB needs to be
flushed.

In short: the generic RCU page-table freeing code is incorrect for the
CRST entries, in particular the check for mm_users < 2 is troublesome.

This is applicable to 3.0+ kernels.

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

S390: KEYS: Enable the compat keyctl wrapper on s390x

2012-03-12T19:31:23+00:00

commit 1d057720609ed052a6371fe1d53300e5e6328e94 upstream.

Enable the compat keyctl wrapper on s390x so that 32-bit s390 userspace can
call the keyctl() syscall.

There's an s390x assembly wrapper that truncates all the register values to
32-bits and this then calls compat_sys_keyctl() - but the latter only exists if
CONFIG_KEYS_COMPAT is enabled, and the s390 Kconfig doesn't enable it.

Without this patch, 32-bit calls to the keyctl() syscall are given an ENOSYS
error:

	[root@devel4 ~]# keyctl show
	Session Keyring
	-3: key inaccessible (Function not implemented)

Signed-off-by: David Howells 
Acked-by: dan@danny.cz
Cc: Carsten Otte 
Reviewed-by: Christian Borntraeger 
Cc: linux-s390@vger.kernel.org
Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky 
Signed-off-by: Greg Kroah-Hartman

compat: fix compile breakage on s390

2012-03-12T19:31:22+00:00

commit 048cd4e51d24ebf7f3552226d03c769d6ad91658 upstream.

The new is_compat_task() define for the !COMPAT case in
include/linux/compat.h conflicts with a similar define in
arch/s390/include/asm/compat.h.

This is the minimal patch which fixes the build issues.

Signed-off-by: Heiko Carstens 
Signed-off-by: Linus Torvalds 
Cc: Jonathan Nieder 
Signed-off-by: Greg Kroah-Hartman

S390: correct ktime to tod clock comparator conversion

2012-03-01T00:30:53+00:00

commit cf1eb40f8f5ea12c9e569e7282161fc7f194fd62 upstream.

The conversion of the ktime to a value suitable for the clock comparator
does not take changes to wall_to_monotonic into account. In fact the
conversion just needs the boot clock (sched_clock_base_cc) and the
total_sleep_time.

This is applicable to 3.2+ kernels.

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

procfs: do not confuse jiffies with cputime64_t

2011-12-30T00:31:57+00:00

Commit 2a95ea6c0d129b4 ("procfs: do not overflow get_{idle,iowait}_time
for nohz") did not take into account that one some architectures jiffies
and cputime use different units.

This causes get_idle_time() to return numbers in the wrong units, making
the idle time fields in /proc/stat wrong.

Instead of converting the usec value returned by
get_cpu_{idle,iowait}_time_us to units of jiffies, use the new function
usecs_to_cputime64 to convert it to the correct unit of cputime64_t.

Signed-off-by: Andreas Schwab 
Acked-by: Michal Hocko 
Cc: Arnd Bergmann 
Cc: "Artem S. Tashkinov" 
Cc: Dave Jones 
Cc: Alexey Dobriyan 
Cc: Thomas Gleixner 
Cc: "Luck, Tony" 
Cc: Benjamin Herrenschmidt 
Cc: Martin Schwidefsky 
Cc: Heiko Carstens 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

oprofile: Fix uninitialized memory access when writing to writing to oprofilefs

2011-12-19T16:18:43+00:00

If oprofilefs_ulong_from_user() is called with count equals
zero, *val remains unchanged. Depending on the implementation it
might be uninitialized.

Change oprofilefs_ulong_from_user()'s interface to return count
on success. Thus, we are able to return early if count equals
zero which avoids using *val uninitialized. Fixing all users of
oprofilefs_ulong_ from_user().

This follows write syscall implementation when count is zero:
"If count is zero ... [and if] no errors are detected, 0 will be
returned without causing any other effect." (man 2 write)

Reported-By: Mike Waychison 
Signed-off-by: Robert Richter 
Cc: Andrew Morton 
Cc: 
Cc: oprofile-list 
Link: http://lkml.kernel.org/r/20111219153830.GH16765@erda.amd.com
Signed-off-by: Ingo Molnar