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Diffstat (limited to 'Documentation/arm/swp_emulation.rst')
| -rw-r--r-- | Documentation/arm/swp_emulation.rst | 27 |
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diff --git a/Documentation/arm/swp_emulation.rst b/Documentation/arm/swp_emulation.rst deleted file mode 100644 index 6a608a9c3715..000000000000 --- a/Documentation/arm/swp_emulation.rst +++ /dev/null @@ -1,27 +0,0 @@ -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. |