linux-stable.git/arch/powerpc/kernel, branch v3.0.58

powerpc: Keep thread.dscr and thread.dscr_inherit in sync

2012-12-17T18:49:05+00:00

commit 00ca0de02f80924dfff6b4f630e1dff3db005e35 upstream.

When we update the DSCR either via emulation of mtspr(DSCR) or via
a change to dscr_default in sysfs we don't update thread.dscr.
We will eventually update it at context switch time but there is
a period where thread.dscr is incorrect.

If we fork at this point we will copy the old value of thread.dscr
into the child. To avoid this, always keep thread.dscr in sync with
reality.

This issue was found with the following testcase:

http://ozlabs.org/~anton/junkcode/dscr_inherit_test.c

Signed-off-by: Anton Blanchard 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Haren Myneni 
Signed-off-by: Greg Kroah-Hartman

powerpc: Update DSCR on all CPUs when writing sysfs dscr_default

2012-12-17T18:49:05+00:00

commit 1b6ca2a6fe56e7697d57348646e07df08f43b1bb upstream.

Writing to dscr_default in sysfs doesn't actually change the DSCR -
we rely on a context switch on each CPU to do the work. There is no
guarantee we will get a context switch in a reasonable amount of time
so fire off an IPI to force an immediate change.

This issue was found with the following test case:

http://ozlabs.org/~anton/junkcode/dscr_explicit_test.c

Signed-off-by: Anton Blanchard 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Haren Myneni 
Signed-off-by: Greg Kroah-Hartman

powerpc/ptrace: Fix build with gcc 4.6

2012-12-17T18:49:02+00:00

commit e69b742a6793dc5bf16f6eedca534d4bc10d68b2 upstream.

gcc (rightfully) complains that we are accessing beyond the
end of the fpr array (we do, to access the fpscr).

The only sane thing to do (whether anything in that code can be
called remotely sane is debatable) is to special case fpscr and
handle it as a separate statement.

I initially tried to do it it by making the array access conditional
to index < PT_FPSCR and using a 3rd else leg but for some reason gcc
was unable to understand it and still spewed the warning.

So I ended up with something a tad more intricated but it seems to
build on 32-bit and on 64-bit with and without VSX.

Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Michael Neuling 
Signed-off-by: Greg Kroah-Hartman

powerpc: Restore correct DSCR in context switch

2012-09-14T17:00:49+00:00

commit 714332858bfd40dcf8f741498336d93875c23aa7 upstream.

During a context switch we always restore the per thread DSCR value.
If we aren't doing explicit DSCR management
(ie thread.dscr_inherit == 0) and the default DSCR changed while
the process has been sleeping we end up with the wrong value.

Check thread.dscr_inherit and select the default DSCR or per thread
DSCR as required.

This was found with the following test case, when running with
more threads than CPUs (ie forcing context switching):

http://ozlabs.org/~anton/junkcode/dscr_default_test.c

With the four patches applied I can run a combination of all
test cases successfully at the same time:

http://ozlabs.org/~anton/junkcode/dscr_default_test.c
http://ozlabs.org/~anton/junkcode/dscr_explicit_test.c
http://ozlabs.org/~anton/junkcode/dscr_inherit_test.c

Signed-off-by: Anton Blanchard 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Greg Kroah-Hartman

powerpc: Fix DSCR inheritance in copy_thread()

2012-09-14T17:00:49+00:00

commit 1021cb268b3025573c4811f1dee4a11260c4507b upstream.

If the default DSCR is non zero we set thread.dscr_inherit in
copy_thread() meaning the new thread and all its children will ignore
future updates to the default DSCR. This is not intended and is
a change in behaviour that a number of our users have hit.

We just need to inherit thread.dscr and thread.dscr_inherit from
the parent which ends up being much simpler.

This was found with the following test case:

http://ozlabs.org/~anton/junkcode/dscr_default_test.c

Signed-off-by: Anton Blanchard 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Greg Kroah-Hartman

powerpc: Fix wrong divisor in usecs_to_cputime

2012-08-09T15:27:34+00:00

commit 9f5072d4f63f28d30d343573830ac6c85fc0deff upstream.

Commit d57af9b (taskstats: use real microsecond granularity for CPU times)
renamed msecs_to_cputime to usecs_to_cputime, but failed to update all
numbers on the way.  This causes nonsensical cpu idle/iowait values to be
displayed in /proc/stat (the only user of usecs_to_cputime so far).

This also renames __cputime_msec_factor to __cputime_usec_factor, adapting
its value and using it directly in cputime_to_usecs instead of doing two
multiplications.

Signed-off-by: Andreas Schwab 
Acked-by: Anton Blanchard 
Signed-off-by: Benjamin Herrenschmidt 
Cc: Michal Hocko 
Signed-off-by: Greg Kroah-Hartman

powerpc/ftrace: Fix assembly trampoline register usage

2012-08-09T15:27:33+00:00

commit fd5a42980e1cf327b7240adf5e7b51ea41c23437 upstream.

Just like the module loader, ftrace needs to be updated to use r12
instead of r11 with newer gcc's.

Signed-off-by: Roger Blofeld 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Paul Gortmaker 
Signed-off-by: Greg Kroah-Hartman

powerpc: Fix kernel panic during kernel module load

2012-06-17T18:23:10+00:00

commit 3c75296562f43e6fbc6cddd3de948a7b3e4e9bcf upstream.

This fixes a problem which can causes kernel oopses while loading
a kernel module.

According to the PowerPC EABI specification, GPR r11 is assigned
the dedicated function to point to the previous stack frame.
In the powerpc-specific kernel module loader, do_plt_call()
(in arch/powerpc/kernel/module_32.c), GPR r11 is also used
to generate trampoline code.

This combination crashes the kernel, in the case where the compiler
chooses to use a helper function for saving GPRs on entry, and the
module loader has placed the .init.text section far away from the
.text section, meaning that it has to generate a trampoline for
functions in the .init.text section to call the GPR save helper.
Because the trampoline trashes r11, references to the stack frame
using r11 can cause an oops.

The fix just uses GPR r12 instead of GPR r11 for generating the
trampoline code.  According to the statements from Freescale, this is
safe from an EABI perspective.

I've tested the fix for kernel 2.6.33 on MPC8541.

Signed-off-by: Steffen Rumler 
[paulus@samba.org: reworded the description]
Signed-off-by: Paul Mackerras 
Signed-off-by: Greg Kroah-Hartman

powerpc/perf: power_pmu_start restores incorrect values, breaking frequency events

2012-03-01T00:33:39+00:00

commit 9a45a9407c69d068500923480884661e2b9cc421 upstream.

perf on POWER stopped working after commit e050e3f0a71b (perf: Fix
broken interrupt rate throttling). That patch exposed a bug in
the POWER perf_events code.

Since the PMCs count upwards and take an exception when the top bit
is set, we want to write 0x80000000 - left in power_pmu_start. We were
instead programming in left which effectively disables the counter
until we eventually hit 0x80000000. This could take seconds or longer.

With the patch applied I get the expected number of samples:

          SAMPLE events:       9948

Signed-off-by: Anton Blanchard 
Acked-by: Paul Mackerras 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Greg Kroah-Hartman

powerpc/time: Handle wrapping of decrementer

2012-01-12T19:35:02+00:00

commit 37fb9a0231ee43d42d069863bdfd567fca2b61af upstream.

When re-enabling interrupts we have code to handle edge sensitive
decrementers by resetting the decrementer to 1 whenever it is negative.
If interrupts were disabled long enough that the decrementer wrapped to
positive we do nothing. This means interrupts can be delayed for a long
time until it finally goes negative again.

While we hope interrupts are never be disabled long enough for the
decrementer to go positive, we have a very good test team that can
drive any kernel into the ground. The softlockup data we get back
from these fails could be seconds in the future, completely missing
the cause of the lockup.

We already keep track of the timebase of the next event so use that
to work out if we should trigger a decrementer exception.

Signed-off-by: Anton Blanchard 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Greg Kroah-Hartman