Based on kernel version 4.16.1. Page generated on 2018-04-09 11:52 EST.
1 Software emulation of deprecated SWP instruction (CONFIG_SWP_EMULATE) 2 --------------------------------------------------------------------- 3 4 ARMv6 architecture deprecates use of the SWP/SWPB instructions, and recommeds 5 moving to the load-locked/store-conditional instructions LDREX and STREX. 6 7 ARMv7 multiprocessing extensions introduce the ability to disable these 8 instructions, triggering an undefined instruction exception when executed. 9 Trapped instructions are emulated using an LDREX/STREX or LDREXB/STREXB 10 sequence. If a memory access fault (an abort) occurs, a segmentation fault is 11 signalled to the triggering process. 12 13 /proc/cpu/swp_emulation holds some statistics/information, including the PID of 14 the last process to trigger the emulation to be invocated. For example: 15 --- 16 Emulated SWP: 12 17 Emulated SWPB: 0 18 Aborted SWP{B}: 1 19 Last process: 314 20 --- 21 22 NOTE: when accessing uncached shared regions, LDREX/STREX rely on an external 23 transaction monitoring block called a global monitor to maintain update 24 atomicity. If your system does not implement a global monitor, this option can 25 cause programs that perform SWP operations to uncached memory to deadlock, as 26 the STREX operation will always fail.