Add Kconfig option ARCH_HAVE_NMI_SAFE_CMPXCHG

cmpxchg() is widely used by lockless code, including NMI-safe lockless
code.  But on some architectures, the cmpxchg() implementation is not
NMI-safe, on these architectures the lockless code may need a
spin_trylock_irqsave() based implementation.

This patch adds a Kconfig option: ARCH_HAVE_NMI_SAFE_CMPXCHG, so that
NMI-safe lockless code can depend on it or provide different
implementation according to it.

On many architectures, cmpxchg is only NMI-safe for several specific
operand sizes. So, ARCH_HAVE_NMI_SAFE_CMPXCHG define in this patch
only guarantees cmpxchg is NMI-safe for sizeof(unsigned long).

Signed-off-by: Huang Ying <[email protected]>
Acked-by: Mike Frysinger <[email protected]>
Acked-by: Paul Mundt <[email protected]>
Acked-by: Hans-Christian Egtvedt <[email protected]>
Acked-by: Benjamin Herrenschmidt <[email protected]>
Acked-by: Chris Metcalf <[email protected]>
Acked-by: Richard Henderson <[email protected]>
CC: Mikael Starvik <[email protected]>
Acked-by: David Howells <[email protected]>
CC: Yoshinori Sato <[email protected]>
CC: Tony Luck <[email protected]>
CC: Hirokazu Takata <[email protected]>
CC: Geert Uytterhoeven <[email protected]>
CC: Michal Simek <[email protected]>
Acked-by: Ralf Baechle <[email protected]>
CC: Kyle McMartin <[email protected]>
CC: Martin Schwidefsky <[email protected]>
CC: Chen Liqin <[email protected]>
CC: "David S. Miller" <[email protected]>
CC: Ingo Molnar <[email protected]>
CC: Chris Zankel <[email protected]>
Signed-off-by: Len Brown <[email protected]>

0 files changed, 0 insertions, 0 deletions