Re: [PATCH] RISC-V: Add CONFIG_PREEMPT=y to defconfig

From: Guenter Roeck <linux@roeck-us.net>
To: Palmer Dabbelt <palmer@sifive.com>
Cc: linux-riscv@lists.infradead.org, Albert Ou <aou@eecs.berkeley.edu>
Subject: Re: [PATCH] RISC-V: Add CONFIG_PREEMPT=y to defconfig
Date: Wed, 19 Dec 2018 17:45:11 -0800	[thread overview]
Message-ID: <20181220014511.GA24845@roeck-us.net> (raw)

On Wed, Nov 21, 2018 at 10:58:05AM -0800, Palmer Dabbelt wrote:
> I don't remember who suggested this, but I was talking to someone at
> Plumbers about all the horrible bugs we've had lurking around in our
> port despite it still getting to userspace and they suggested that I
> enable CONFIG_PREEMPT in our defconfig as it'll help shake out more
> issues.
> 
> This patch enables CONFIG_PREEMPT in the single RISC-V defconfig.  It
> still passes my tests (ie, booting Fedora on QEMU).  Maybe I'm too
> paranoid, but I still don't trust our port enough to just pull the
> trigger on this without at least accumulating some "Tested-by"s on it.
> 
> Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

I can only give you a

Fails-miserably-for: Guenter Roeck <linux@roeck-us.net>

Not the new defconfig itself, but the new defconfig plus a variety of
selftest options. I don't know what exactly is failing, but here is
my list of enabled selftests on top of defconfig:

CONFIG_CRYPTO_MANAGER_DISABLE_TESTS=y
CONFIG_CRC32_SELFTEST=y
CONFIG_DEBUG_LOCKING_API_SELFTESTS=y
CONFIG_DEBUG_NMI_SELFTEST=y
CONFIG_DEBUG_RODATA_TEST=y
CONFIG_DEBUG_TLBFLUSH=y
CONFIG_DMATEST=y
CONFIG_GLOB_SELFTEST=y
CONFIG_OF_UNITTEST=y
CONFIG_PCI_EPF_TEST=y
CONFIG_PCI_ENDPOINT_TEST=y
CONFIG_PROVE_LOCKING=y
CONFIG_PROVE_RCU=y
CONFIG_RCU_EQS_DEBUG=y
CONFIG_STATIC_KEYS_SELFTEST=y
CONFIG_STRING_SELFTEST=y
CONFIG_TEST_BITMAP=y
CONFIG_TEST_FIRMWARE=y
CONFIG_TEST_SORT=y
CONFIG_TEST_SYSCTL=y
CONFIG_TEST_UUID=y
CONFIG_USB_TEST=y
CONFIG_USB_EHSET_TEST_FIXTURE=y
CONFIG_USB_LINK_LAYER_TEST=y
CONFIG_WW_MUTEX_SELFTEST=y
CONFIG_TORTURE_TEST=y
CONFIG_LOCK_TORTURE_TEST=y
CONFIG_RCU_TORTURE_TEST=y
CONFIG_RBTREE_TEST=y
CONFIG_INTERVAL_TREE_TEST=y

Tests pass after disabling those tests (or after reverting your patch).

Guenter

> ---
>  arch/riscv/configs/defconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/configs/defconfig b/arch/riscv/configs/defconfig
> index ef4f15df9adf..8869471af0fc 100644
> --- a/arch/riscv/configs/defconfig
> +++ b/arch/riscv/configs/defconfig
> @@ -1,5 +1,6 @@
>  CONFIG_SYSVIPC=y
>  CONFIG_POSIX_MQUEUE=y
> +CONFIG_PREEMPT=y
>  CONFIG_IKCONFIG=y
>  CONFIG_IKCONFIG_PROC=y
>  CONFIG_CGROUPS=y
> @@ -77,4 +78,3 @@ CONFIG_NFS_V4_2=y
>  CONFIG_ROOT_NFS=y
>  CONFIG_CRYPTO_USER_API_HASH=y
>  CONFIG_PRINTK_TIME=y
> -# CONFIG_RCU_TRACE is not set
> -- 
> 2.7.4

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