linux-toradex.git/arch/arc/kernel, branch v4.4.27

arc: unwind: warn only once if DW2_UNWIND is disabled

2016-08-10T09:49:25+00:00

commit 9bd54517ee86cb164c734f72ea95aeba4804f10b upstream.

If CONFIG_ARC_DW2_UNWIND is disabled every time arc_unwind_core()
gets called following message gets printed in debug console:
----------------->8---------------
CONFIG_ARC_DW2_UNWIND needs to be enabled
----------------->8---------------

That message makes sense if user indeed wants to see a backtrace or
get nice function call-graphs in perf but what if user disabled
unwinder for the purpose? Why pollute his debug console?

So instead we'll warn user about possibly missing feature once and
let him decide if that was what he or she really wanted.

Signed-off-by: Alexey Brodkin 
Signed-off-by: Vineet Gupta 
Signed-off-by: Greg Kroah-Hartman

ARCv2: LLSC: software backoff is NOT needed starting HS2.1c

2016-07-27T16:47:31+00:00

commit b31ac42697bef4a3aa5d0aa42375a55657f57174 upstream.

Signed-off-by: Vineet Gupta 
Signed-off-by: Greg Kroah-Hartman

ARCv2: Check for LL-SC livelock only if LLSC is enabled

2016-07-27T16:47:31+00:00

commit 4d0cb15fccd1db9dac0c964b2ccf10874e69f5b8 upstream.

Signed-off-by: Vineet Gupta 
Signed-off-by: Greg Kroah-Hartman

ARCv2: SMP: Emulate IPI to self using software triggered interrupt

2016-03-03T23:07:28+00:00

commit bb143f814ea488769ca2e79e0b376139cb5f134b upstream.

ARConnect/MCIP Inter-Core-Interrupt module can't send interrupt to
local core. So use core intc capability to trigger software
interrupt to self, using an unsued IRQ #21.

This showed up as csd deadlock with LTP trace_sched on a dual core
system. This test acts as scheduler fuzzer, triggering all sorts of
schedulting activity. Trouble starts with IPI to self, which doesn't get
delivered (effectively lost due to H/w capability), but the msg intended
to be sent remain enqueued in per-cpu @ipi_data.

All subsequent IPIs to this core from other cores get elided due to the
IPI coalescing optimization in ipi_send_msg_one() where a pending msg
implies an IPI already sent and assumes other core is yet to ack it.
After the elided IPI, other core simply goes into csd_lock_wait()
but never comes out as this core never sees the interrupt.

Fixes STAR 9001008624

Cc: Peter Zijlstra 
Signed-off-by: Vineet Gupta 
Signed-off-by: Greg Kroah-Hartman

ARCv2: STAR 9000950267: Handle return from intr to Delay Slot #2

2016-03-03T23:07:28+00:00

commit cbfe74a753e877b49dc54e9b04d5d42230ca0aed upstream.

Returning to delay slot, riding an interrupti, had one loose end.
AUX_USER_SP used for restoring user mode SP upon RTIE was not being
setup from orig task's saved value, causing task to use wrong SP,
leading to ProtV errors.

The reason being:
 - INTERRUPT_EPILOGUE returns to a kernel trampoline, thus not expected to restore it
 - EXCEPTION_EPILOGUE is not used at all

Fix that by restoring AUX_USER_SP explicitly in the trampoline.

This was broken in the original workaround, but the error scenarios got
reduced considerably since v3.14 due to following:

 1. The Linuxthreads.old based userspace at the time caused many more
    exceptions in delay slot than the current NPTL based one.
    Infact with current userspace the error doesn't happen at all.

 2. Return from interrupt (delay slot or otherwise) doesn't get exercised much
    after commit 4de0e52867d8 ("Really Re-enable interrupts to avoid deadlocks")
    since IRQ_ACTIVE.active being clear means most returns are as if from pure
    kernel (even for active interrupts)

Infact the issue only happened in an experimental branch where I was tinkering with
reverted 4de0e52867d8

Fixes: 4255b07f2c9c ("ARCv2: STAR 9000793984: Handle return from intr to Delay Slot")
Signed-off-by: Vineet Gupta 
Signed-off-by: Greg Kroah-Hartman

ARC: dw2 unwind: Catch Dwarf SNAFUs early

2015-12-21T08:31:49+00:00

Instead of seeing empty stack traces, let kernel fail early so dwarf
issues can be fixed sooner

Signed-off-by: Vineet Gupta

ARC: dw2 unwind: Don't bail for CIE.version != 1

2015-12-21T08:31:25+00:00

The rudimentary CIE.version == 3 handling is already present in code
(for return address register specification)

Signed-off-by: Vineet Gupta

Revert "ARC: dw2 unwind: Ignore CIE version !=1 gracefully instead of bailing"

2015-12-21T07:59:44+00:00

Blingly ignoring CIE.version != 1 was a bad idea.
It still leaves "desirability" when running perf with callgraphing where libgcc
symbols might show in hotspot.

More importantly, basic CIE.version == 3 support already exists in code:

|
|   retAddrReg = state.version <= 1 ? *ptr++ : get_uleb128(&ptr, end);
|

Next commit with simply add continue-not-bail for CIE.version != 1

This reverts commit 323f41f9e7d0cb5b1d1586aded6682855f1e646d.

ARC: smp: Rename platform hook @init_cpu_smp -> @init_per_cpu

2015-12-17T07:26:56+00:00

Makes it similar to smp_ops which also has callback with same name

Signed-off-by: Vineet Gupta

ARC: rename smp operation init_irq_cpu() to init_per_cpu()

2015-12-17T07:26:43+00:00

This will better reflect its description i.e. "any needed setup..."
and not just do an "IPI request".

Signed-off-by: Noam Camus 
Acked-by: Vineet Gupta 
Signed-off-by: Vineet Gupta