Messages in this thread | | | Date | Fri, 06 Jul 2018 10:02:35 -0700 | From | pheragu@codeauro ... | Subject | Re: [PATCH] checkpatch: Add exceptions for dsb keyword usage |
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On 2018-07-05 22:45, Mark Rutland wrote: > On Thu, Jul 05, 2018 at 02:14:28PM -0700, Joe Perches wrote: >> On Thu, 2018-07-05 at 11:19 -0700, Prakruthi Deepak Heragu wrote: >> > mb() API can relpace the dsb() API in the kernel code. So, dsb() usage >> > is discouraged. However, there are exceptions when dsb is used in a >> > variable or a function name. Exceptions are when 'dsb' is prefixed with >> > class [-_>*\.] and/or suffixed with class [-_\.;]. > > This is a really confusing way of describing the match behaviour, and > doesn't > explain why this is a big problem. > > In C it's either: > > dsb() > dsb(scope) // e.g. dsb(ish) > > ... where scope is [a-z]*. > > ... which can be matched as something like 'dsb([a-z]*)' if necessary. > >> [] >> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl >> [] >> > @@ -5372,6 +5372,12 @@ sub process { >> > "Avoid line continuations in quoted strings\n" . $herecurr); >> > } >> > >> > +# dsb is too ARMish, and should usually be mb. >> > + if ($line =~ /[^-_>*\.]\bdsb\b[^-_\.;]/) { >> > + WARN("ARM_BARRIER", >> > + "Use of dsb is discouranged: prefer mb.\n" . >> > + $herecurr); >> > + } >> >> This patch is whitespace damaged with a spelling error. >> >> Also, if this is reasonable test, and I don't know >> that it is, it should be cc'd to the linux-arm list >> linux-arm-kernel@lists.infradead.org >> >> Also, I suggest 2 tests, one for .S files and >> another for .[ch] files, and this be made specific >> to arch/arm... files >> >> Something like: >> >> if ($realfile =~ @^arch/arm@ && >> ($realfile =~ /\.S$/ && $line =~ /\bdsb\b/) || >> ($realfile =~ /\.[ch]$/ && $line =~ /\bdsb\s*\(/)) { >> WARN("ARM_DSB", >> "Prefer mb over dsb as an ARM memory barrier\n" . $herecurr); >> } >> >> ARM people, is this reasonable? > > I don't think this is a big deal today. > > For code under arch/{arm,arm64}, it's perfectly reasonable to use dsb. > > For code *ouside* of arch/{arm,arm64}, there are a number of cases > where we > want to use dsb(), e.g. when dealing with architectural drivers that > require > special barriers, or for common code shared across arm and arm64. > > It doesn't look like this is a big problem today, anyhow: > > [mark@salmiak:~/src/linux]% git grep -w 'dsb(.*)' -- ^arch > drivers/irqchip/irq-armada-370-xp.c: dsb(); > drivers/irqchip/irq-gic-v3-its.c: dsb(ishst); > drivers/irqchip/irq-gic-v3-its.c: dsb(ishst); > drivers/irqchip/irq-gic-v3-its.c: dsb(sy); > drivers/irqchip/irq-gic-v3-its.c: dsb(sy); > drivers/irqchip/irq-gic-v3-its.c: dsb(sy); > drivers/mtd/nand/raw/cmx270_nand.c: dsb(); > drivers/mtd/nand/raw/cmx270_nand.c: dsb(); > drivers/mtd/nand/raw/cmx270_nand.c: dsb(); > drivers/mtd/nand/raw/cmx270_nand.c: dsb(); > drivers/mtd/nand/raw/cmx270_nand.c: dsb(); > drivers/perf/arm_spe_pmu.c: dsb(nsh); > drivers/perf/arm_spe_pmu.c: dsb(nsh); > drivers/power/reset/arm-versatile-reboot.c: dsb(); > drivers/soc/rockchip/pm_domains.c: dsb(sy); > drivers/soc/rockchip/pm_domains.c: dsb(sy); > drivers/staging/mt7621-mmc/sd.c: //dsb(); /* --- by chhung */ > drivers/staging/mt7621-mmc/sd.c: //dsb(); /* --- by chhung */ > drivers/staging/vc04_services/interface/vchiq_arm/vchiq.h:#define > dsb(a) > drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c: > dsb(sy); /* data barrier operation */ > drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c: > dsb(sy); > drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.h: do { > debug_ptr[DEBUG_ ## d] = __LINE__; dsb(sy); } while (0) > drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.h: do { > debug_ptr[DEBUG_ ## d] = (v); dsb(sy); } while (0) > drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.h: do { > debug_ptr[DEBUG_ ## d]++; dsb(sy); } while (0) > virt/kvm/arm/hyp/vgic-v3-sr.c: dsb(sy); > virt/kvm/arm/hyp/vgic-v3-sr.c: dsb(sy); > virt/kvm/arm/hyp/vgic-v3-sr.c: dsb(sy); > > Thanks, > Mark. Thanks Mark. I appreciate your feedback.
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