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Diffstat (limited to 'Documentation/arm/swp_emulation')
| -rw-r--r-- | Documentation/arm/swp_emulation | 27 |
1 files changed, 0 insertions, 27 deletions
diff --git a/Documentation/arm/swp_emulation b/Documentation/arm/swp_emulation deleted file mode 100644 index af903d22fd93..000000000000 --- a/Documentation/arm/swp_emulation +++ /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. - |