linux-toradex.git/arch/arc, branch v3.12.29

ARC: Implement ptrace(PTRACE_GET_THREAD_AREA)

2014-07-29T15:01:49+00:00

commit a4b6cb735b25aa84a462a1985e3e43bebaf5beb4 upstream.

This patch adds implementation of GET_THREAD_AREA ptrace request type. This
is required by GDB to debug NPTL applications.

Signed-off-by: Anton Kolesov 
Signed-off-by: Vineet Gupta 
Signed-off-by: Jiri Slaby

ARC: !PREEMPT: Ensure Return to kernel mode is IRQ safe

2014-05-15T07:55:56+00:00

commit 8aa9e85adac609588eeec356e5a85059b3b819ba upstream.

There was a very small race window where resume to kernel mode from a
Exception Path (or pure kernel mode which is true for most of ARC
exceptions anyways), was not disabling interrupts in restore_regs,
clobbering the exception regs

Anton found the culprit call flow (after many sleepless nights)

| 1. we got a Trap from user land
| 2. started to service it.
| 3. While doing some stuff on user-land memory (I think it is padzero()),
|     we got a DataTlbMiss
| 4. On return from it we are taking "resume_kernel_mode" path
| 5. NEED_RESHED is not set, so we go to "return from exception" path in
|     restore regs.
| 6. there seems to be IRQ happening

Signed-off-by: Vineet Gupta 
Cc: Anton Kolesov 
Cc: Francois Bedard 
Signed-off-by: Linus Torvalds 
Signed-off-by: Jiri Slaby

ARC: Remove ARC_HAS_COH_RTSC

2014-05-15T07:55:55+00:00

commit d345ea2892ae7a2b70f84cf881c20731e43e4993 upstream.

The symbol is an orphan, get rid of it.

Fixes: 7d0857a54aed ("ARC: [SMP] Disallow RTSC")
Signed-off-by: Richard Weinberger 
Acked-by: Paul Bolle 
Signed-off-by: Vineet Gupta 
Signed-off-by: Jiri Slaby

ARC: [nsimosci] Unbork console

2014-04-18T09:07:21+00:00

commit 61fb4bfc010b0d2940f7fd87acbce6a0f03217cb upstream.

Despite the switch to right UART driver (prev patch), serial console
still doesn't work due to missing CONFIG_SERIAL_OF_PLATFORM

Also fix the default cmdline in DT to not refer to out-of-tree
ARC framebuffer driver for console.

Signed-off-by: Vineet Gupta 
Cc: Francois Bedard 
Signed-off-by: Jiri Slaby

ARC: [nsimosci] Change .dts to use generic 8250 UART

2014-04-18T09:07:20+00:00

commit 6eda477b3c54b8236868c8784e5e042ff14244f0 upstream.

The Synopsys APB DW UART has a couple of special features that are not
in the System C model. In 3.8, the 8250_dw driver didn't really use these
features, but from 3.9 onwards, the 8250_dw driver has become incompatible
with our model.

Signed-off-by: Mischa Jonker 
Signed-off-by: Vineet Gupta 
Cc: Francois Bedard 
Signed-off-by: Jiri Slaby

ARC: Incorrect mm reference used in vmalloc fault handler

2013-11-02T17:27:04+00:00

A vmalloc fault needs to sync up PGD/PTE entry from init_mm to current
task's "active_mm".  ARC vmalloc fault handler however was using mm.

A vmalloc fault for non user task context (actually pre-userland, from
init thread's open for /dev/console) caused the handler to deref NULL mm
(for mm->pgd)

The reasons it worked so far is amazing:

1. By default (!SMP), vmalloc fault handler uses a cached value of PGD.
   In SMP that MMU register is repurposed hence need for mm pointer deref.

2. In pre-3.12 SMP kernel, the problem triggering vmalloc didn't exist in
   pre-userland code path - it was introduced with commit 20bafb3d23d108bc
   "n_tty: Move buffers into n_tty_data"

Signed-off-by: Vineet Gupta 
Cc: Gilad Ben-Yossef 
Cc: Noam Camus 
Cc: stable@vger.kernel.org    #3.10 and 3.11
Cc: Peter Hurley 
Signed-off-by: Linus Torvalds

ARC: Ignore ptrace SETREGSET request for synthetic register "stop_pc"

2013-10-12T06:30:36+00:00

ARCompact TRAP_S insn used for breakpoints, commits before exception is
taken (updating architectural PC). So ptregs->ret contains next-PC and
not the breakpoint PC itself. This is different from other restartable
exceptions such as TLB Miss where ptregs->ret has exact faulting PC.
gdb needs to know exact-PC hence ARC ptrace GETREGSET provides for
@stop_pc which returns ptregs->ret vs. EFA depending on the
situation.

However, writing stop_pc (SETREGSET request), which updates ptregs->ret
doesn't makes sense stop_pc doesn't always correspond to that reg as
described above.

This was not an issue so far since user_regs->ret / user_regs->stop_pc
had same value and both writing to ptregs->ret was OK, needless, but NOT
broken, hence not observed.

With gdb "jump", they diverge, and user_regs->ret updating ptregs is
overwritten immediately with stop_pc, which this patch fixes.

Reported-by: Anton Kolesov 
Signed-off-by: Vineet Gupta

ARC: Fix signal frame management for SA_SIGINFO

2013-10-03T04:13:56+00:00

Previously, when a signal was registered with SA_SIGINFO, parameters 2
and 3 of the signal handler were written to registers r1 and r2 before
the register set was saved. This led to corruption of these two
registers after returning from the signal handler (the wrong values were
restored).
With this patch, registers are now saved before any parameters are
passed, thus maintaining the processor state from before signal entry.

Signed-off-by: Christian Ruppert 
Signed-off-by: Vineet Gupta

ARC: Use clockevents_config_and_register over clockevents_register_device

2013-09-27T10:58:48+00:00

clockevents_config_and_register is more clever and correct than doing it
by hand; so use it.

[vgupta: fixed build failure due to missing ; in patch]

Signed-off-by: Uwe Kleine-König 
Signed-off-by: Vineet Gupta

ARC: Workaround spinlock livelock in SMP SystemC simulation

2013-09-27T10:58:48+00:00

Some ARC SMP systems lack native atomic R-M-W (LLOCK/SCOND) insns and
can only use atomic EX insn (reg with mem) to build higher level R-M-W
primitives. This includes a SystemC based SMP simulation model.

So rwlocks need to use a protecting spinlock for atomic cmp-n-exchange
operation to update reader(s)/writer count.

The spinlock operation itself looks as follows:

	mov reg, 1		; 1=locked, 0=unlocked
retry:
	EX reg, [lock]		; load existing, store 1, atomically
	BREQ reg, 1, rety	; if already locked, retry

In single-threaded simulation, SystemC alternates between the 2 cores
with "N" insn each based scheduling. Additionally for insn with global
side effect, such as EX writing to shared mem, a core switch is
enforced too.

Given that, 2 cores doing a repeated EX on same location, Linux often
got into a livelock e.g. when both cores were fiddling with tasklist
lock (gdbserver / hackbench) for read/write respectively as the
sequence diagram below shows:

           core1                                   core2
         --------                                --------
1. spin lock [EX r=0, w=1] - LOCKED
2. rwlock(Read)            - LOCKED
3. spin unlock  [ST 0]     - UNLOCKED
                                         spin lock [EX r=0,w=1] - LOCKED
                      -- resched core 1----

5. spin lock [EX r=1] - ALREADY-LOCKED

                      -- resched core 2----
6.                                       rwlock(Write) - READER-LOCKED
7.                                       spin unlock [ST 0]
8.                                       rwlock failed, retry again

9.                                       spin lock  [EX r=0, w=1]
                      -- resched core 1----

10  spinlock locked in #9, retry #5
11. spin lock [EX gets 1]
                      -- resched core 2----
...
...

The fix was to unlock using the EX insn too (step 7), to trigger another
SystemC scheduling pass which would let core1 proceed, eliding the
livelock.

Signed-off-by: Vineet Gupta