mirror of
https://github.com/torvalds/linux.git
synced 2024-12-05 02:23:16 +00:00
dc7a12bdfc
Converts ARM the text files to ReST, preparing them to be an architecture book. The conversion is actually: - add blank lines and identation in order to identify paragraphs; - fix tables markups; - add some lists markups; - mark literal blocks; - adjust title markups. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Reviewed-by Corentin Labbe <clabbe.montjoie@gmail.com> # For sun4i-ss
28 lines
1.2 KiB
ReStructuredText
28 lines
1.2 KiB
ReStructuredText
Software emulation of deprecated SWP instruction (CONFIG_SWP_EMULATE)
|
|
---------------------------------------------------------------------
|
|
|
|
ARMv6 architecture deprecates use of the SWP/SWPB instructions, and recommeds
|
|
moving to the load-locked/store-conditional instructions LDREX and STREX.
|
|
|
|
ARMv7 multiprocessing extensions introduce the ability to disable these
|
|
instructions, triggering an undefined instruction exception when executed.
|
|
Trapped instructions are emulated using an LDREX/STREX or LDREXB/STREXB
|
|
sequence. If a memory access fault (an abort) occurs, a segmentation fault is
|
|
signalled to the triggering process.
|
|
|
|
/proc/cpu/swp_emulation holds some statistics/information, including the PID of
|
|
the last process to trigger the emulation to be invocated. For example::
|
|
|
|
Emulated SWP: 12
|
|
Emulated SWPB: 0
|
|
Aborted SWP{B}: 1
|
|
Last process: 314
|
|
|
|
|
|
NOTE:
|
|
when accessing uncached shared regions, LDREX/STREX rely on an external
|
|
transaction monitoring block called a global monitor to maintain update
|
|
atomicity. If your system does not implement a global monitor, this option can
|
|
cause programs that perform SWP operations to uncached memory to deadlock, as
|
|
the STREX operation will always fail.
|