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Date: Thu, 4 Dec 2014 22:30:20 -0500 From: Pranith Kumar <bobby.prani@...il.com> To: Lai Jiangshan <laijs@...fujitsu.com> Cc: Paul McKenney <paulmck@...ux.vnet.ibm.com>, LKML <linux-kernel@...r.kernel.org>, Josh Triplett <josh@...htriplett.org> Subject: Re: [PATCH] tinification: Make SRCU optional by using CONFIG_SRCU On Thu, Dec 4, 2014 at 9:05 PM, Lai Jiangshan <laijs@...fujitsu.com> wrote: > On 12/05/2014 08:11 AM, Paul E. McKenney wrote: >> On Thu, Dec 04, 2014 at 06:50:24PM -0500, Pranith Kumar wrote: >>> SRCU is not necessary to be compiled by default in all cases. For tinification >>> efforts not compiling SRCU unless necessary is desirable. >>> >>> The current patch tries to make compiling SRCU optional by introducing a new >>> Kconfig option CONFIG_SRCU which is selected when any of the components making >>> use of SRCU are selected. >>> >>> If we do not select CONFIG_SRCU, srcu.o will not be compiled at all. >>> >>> text data bss dec hex filename >>> 2007 0 0 2007 7d7 kernel/rcu/srcu.o >>> >>> Size of arch/powerpc/boot/zImage changes from >>> >>> text data bss dec hex filename >>> 831552 64180 23944 919676 e087c arch/powerpc/boot/zImage : before >>> 829504 64180 23952 917636 e0084 arch/powerpc/boot/zImage : after >>> >>> so the savings are about ~2000 bytes. >>> >>> Signed-off-by: Pranith Kumar <bobby.prani@...il.com> >>> CC: Paul McKenney <paulmck@...ux.vnet.ibm.com> >>> CC: Josh Triplett <josh@...htriplett.org> >> >> I have queued this for testing. >> >> Josh, does this look reasonable to you? >> >> Lai, any issues? >> >> Thanx, Paul >> >>> --- >>> arch/arm/kvm/Kconfig | 1 + >>> arch/arm64/kvm/Kconfig | 1 + >>> arch/ia64/kvm/Kconfig | 1 + >>> arch/mips/kvm/Kconfig | 1 + >>> arch/powerpc/kvm/Kconfig | 1 + >>> arch/s390/kvm/Kconfig | 1 + >>> arch/tile/kvm/Kconfig | 1 + >>> arch/x86/Kconfig | 1 + >>> arch/x86/kvm/Kconfig | 1 + >>> drivers/clk/Kconfig | 1 + >>> drivers/cpufreq/Kconfig | 1 + >>> drivers/devfreq/Kconfig | 1 + >>> drivers/md/Kconfig | 1 + >>> drivers/net/Kconfig | 1 + >>> fs/btrfs/Kconfig | 1 + >>> fs/notify/Kconfig | 1 + >>> init/Kconfig | 10 ++++++++++ >>> kernel/notifier.c | 3 +++ >>> kernel/rcu/Makefile | 3 ++- >>> lib/Kconfig.debug | 1 + >>> mm/Kconfig | 1 + >>> security/tomoyo/Kconfig | 1 + >>> 22 files changed, 34 insertions(+), 1 deletion(-) > > Miss fs/quota/Kconfig? > > ./fs/quota/dquot.c:100: * Operation of reading pointer needs srcu_read_lock(&dquot_srcu), and > ./fs/quota/dquot.c:1609: index = srcu_read_lock(&dquot_srcu); > ./fs/quota/dquot.c:1657: index = srcu_read_lock(&dquot_srcu); > ./fs/quota/dquot.c:1695: index = srcu_read_lock(&dquot_srcu); > ./fs/quota/dquot.c:1724: index = srcu_read_lock(&dquot_srcu); > ./fs/quota/dquot.c:1756: index = srcu_read_lock(&dquot_srcu); > ./fs/quota/dquot.c:1797: index = srcu_read_lock(&dquot_srcu); > ./fs/quota/dquot.c:1827: * protect them by srcu_read_lock(). > > And > > ./drivers/base/power/opp.c:90: struct srcu_notifier_head head; > ./drivers/base/power/opp.c:439: srcu_init_notifier_head(&dev_opp->head); > ./drivers/base/power/opp.c:484: srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_ADD, new_opp); > ./drivers/base/power/opp.c:564: srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_ENABLE, > ./drivers/base/power/opp.c:567: srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_DISABLE, > ./drivers/base/power/opp.c:625:struct srcu_notifier_head *dev_pm_opp_get_notifier(struct device *dev) > > === I've added the above two locations to enable SRCU. > > include/linux/srcu.h and ./include/linux/notifier.h should also use > "#ifdef CONFIG_SRCU .... " > > >>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >>> index ded8a67..1c581a0 100644 >>> --- a/arch/x86/Kconfig >>> +++ b/arch/x86/Kconfig >>> @@ -137,6 +137,7 @@ config X86 >>> select HAVE_ACPI_APEI_NMI if ACPI >>> select ACPI_LEGACY_TABLES_LOOKUP if ACPI >>> select X86_FEATURE_NAMES if PROC_FS >>> + select SRCU > > > > > Why you select SRCU when X86? > The reason is that x86 selects PERF_EVENTS which inturn needs SRCU. We were not sure if SRCU will be recursively enabled when PERF_EVENTS is enabled. >>> >>> +config SRCU >>> + bool "Sleepable form of RCU" > > Why it has a title? Somebody need to select it manually for third party kernel module? Yes, it is a choice given to enable SRCU even when no in-kernel module uses it. > >>> + def_bool n >>> + help >>> + This option selects the sleepable version of RCU. This version >>> + permits arbitrary sleeping or blocking within RCU read-side critical >>> + sections. > > You used "form" and "version" at the same time. I will fix this in the next iteration. > > >>> >>> +#ifdef CONFIG_SRCU >>> /* >>> * SRCU notifier chain routines. Registration and unregistration >>> * use a mutex, and call_chain is synchronized by SRCU (no locks). >>> @@ -528,6 +529,8 @@ void srcu_init_notifier_head(struct srcu_notifier_head *nh) >>> } >>> EXPORT_SYMBOL_GPL(srcu_init_notifier_head); >>> >>> +#endif /* CONFIG_SRCU */ > > Do we need a new CONFIG_SRCU_NOTIFIER ? I am not sure actually. Why not just CONFIG_SRCU like here? -- Pranith -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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