According to create_thread(3): "The new thread does not inherit the creating
thread's alternate signal stack". Since commit f9a3879a (Fix sigaltstack
corruption among cloned threads), current->sas_ss_size is set to 0 for cloned
processes sharing VM with their parent. Don't use the (nonexistent) alternate
signal stack in this case. This has been broken since commit 29c4dfd9 ([XTENSA]
Remove non-rt signal handling).

Fixes the SA_ONSTACK part of the nptl/tst-cancel20 test from uClibc.

Cc: <stable@vger.kernel.org>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

Pull xtensa update from Chris Zankel:
 "Added features:
   - add support for thread local storage (TLS)

   - add accept4 and finit_module syscalls

   - support medium-priority interrupts

   - add support for dc232c processor variant

   - support file-base simulated disk for ISS simulator

  Bug fixes:

   - fix return values returned by the str[n]cmp functions

   - avoid mmap cache aliasing

   - fix handling of 'windowed registers' in ptrace"

* tag 'xtensa-next-20130225' of git://github.com/czankel/xtensa-linux:
  xtensa: add accept4 syscall
  xtensa: add support for TLS
  xtensa: add missing include asm/uaccess.h to checksum.h
  xtensa: do not enable GENERIC_GPIO by default
  xtensa: complete ptrace handling of register windows
  xtensa: add support for oprofile
  xtensa: move spill_registers to traps.h
  xtensa: ISS: add host file-based simulated disk
  xtensa: fix str[n]cmp return value
  xtensa: avoid mmap cache aliasing
  xtensa: add finit_module syscall
  xtensa: pull signal definitions from signal-defs.h
  xtensa: fix ipc_parse_version selection
  xtensa: dispatch medium-priority interrupts
  xtensa: Add config files for Diamond 233L - Rev C processor variant
  xtensa: use new common dtc rule
  xtensa: rename prom_update_property to of_update_property

The Xtensa architecture provides a global register called THREADPTR
for the purpose of Thread Local Storage (TLS) support. This allows us
to use a fairly simple implementation, keeping the thread pointer in
the regset and simply saving and restoring it upon entering/exiting
the from user space.

Signed-off-by: Chris Zankel <chris@zankel.net>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Remove heading and trailing spaces, trim trailing lines, and wrap lines
that are longer than 80 characters.

Signed-off-by: Chris Zankel <chris@zankel.net>

This include is no longer needed.
(seems to be a leftover from try_to_freeze())

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

asm glue checks that

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Obvious brainos spotted by Geert.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Does block_sigmask() + tracehook_signal_handler();  called when
sigframe has been successfully built.  All architectures converted
to it; block_sigmask() itself is gone now (merged into this one).

I'm still not too happy with the signature, but that's a separate
story (IMO we need a structure that would contain signal number +
siginfo + k_sigaction, so that get_signal_to_deliver() would fill one,
signal_delivered(), handle_signal() and probably setup...frame() -
take one).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Only 3 out of 63 do not.  Renamed the current variant to __set_current_blocked(),
added set_current_blocked() that will exclude unblockable signals, switched
open-coded instances to it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>