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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2011-01-07 03:50:35 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-01-07 03:50:35 +0300 |
| commit | 3c0cb7c31c206aaedb967e44b98442bbeb17a6c4 (patch) | |
| tree | 3ecba45d7ffae4fba4a5aafaef4af5b0b1105bde /Documentation | |
| parent | f70f5b9dc74ca7d0a64c4ead3fb28da09dc1b234 (diff) | |
| parent | 404a02cbd2ae8bf256a2fa1169bdfe86bb5ebb34 (diff) | |
| download | linux-3c0cb7c31c206aaedb967e44b98442bbeb17a6c4.tar.xz | |
Merge branch 'devel' of master.kernel.org:/home/rmk/linux-2.6-arm
* 'devel' of master.kernel.org:/home/rmk/linux-2.6-arm: (416 commits)
ARM: DMA: add support for DMA debugging
ARM: PL011: add DMA burst threshold support for ST variants
ARM: PL011: Add support for transmit DMA
ARM: PL011: Ensure IRQs are disabled in UART interrupt handler
ARM: PL011: Separate hardware FIFO size from TTY FIFO size
ARM: PL011: Allow better handling of vendor data
ARM: PL011: Ensure error flags are clear at startup
ARM: PL011: include revision number in boot-time port printk
ARM: vexpress: add sched_clock() for Versatile Express
ARM i.MX53: Make MX53 EVK bootable
ARM i.MX53: Some bug fix about MX53 MSL code
ARM: 6607/1: sa1100: Update platform device registration
ARM: 6606/1: sa1100: Fix platform device registration
ARM i.MX51: rename IPU irqs
ARM i.MX51: Add ipu clock support
ARM: imx/mx27_3ds: Add PMIC support
ARM: DMA: Replace page_to_dma()/dma_to_page() with pfn_to_dma()/dma_to_pfn()
mx51: fix usb clock support
MX51: Add support for usb host 2
arch/arm/plat-mxc/ehci.c: fix errors/typos
...
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/arm/00-INDEX | 2 | ||||
| -rw-r--r-- | Documentation/arm/swp_emulation | 27 |
2 files changed, 29 insertions, 0 deletions
diff --git a/Documentation/arm/00-INDEX b/Documentation/arm/00-INDEX index ecf7d04bca26..91c24a1e8a9e 100644 --- a/Documentation/arm/00-INDEX +++ b/Documentation/arm/00-INDEX @@ -34,3 +34,5 @@ memory.txt - description of the virtual memory layout nwfpe/ - NWFPE floating point emulator documentation +swp_emulation + - SWP/SWPB emulation handler/logging description diff --git a/Documentation/arm/swp_emulation b/Documentation/arm/swp_emulation new file mode 100644 index 000000000000..af903d22fd93 --- /dev/null +++ b/Documentation/arm/swp_emulation @@ -0,0 +1,27 @@ +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. + |