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3da4390bcd
linux/arch/arm64
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Will Deacon 3da4390bcd arm64: perf: Don't register user access sysctl handler multiple times 
Commit e201260081 ("arm64: perf: Add userspace counter access disable
switch") introduced a new 'perf_user_access' sysctl file to enable and
disable direct userspace access to the PMU counters. Sadly, Geert
reports that on his big.LITTLE SoC ('Renesas Salvator-XS w/ R-Car H3'),
the file is created for each PMU type probed, resulting in a splat
during boot:

  | hw perfevents: enabled with armv8_cortex_a53 PMU driver, 7 counters available
  | sysctl duplicate entry: /kernel//perf_user_access
  | CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.16.0-rc3-arm64-renesas-00003-ge2012600810c #1420
  | Hardware name: Renesas Salvator-X 2nd version board based on r8a77951 (DT)
  | Call trace:
  |  dump_backtrace+0x0/0x190
  |  show_stack+0x14/0x20
  |  dump_stack_lvl+0x88/0xb0
  |  dump_stack+0x14/0x2c
  |  __register_sysctl_table+0x384/0x818
  |  register_sysctl+0x20/0x28
  |  armv8_pmu_init.constprop.0+0x118/0x150
  |  armv8_a57_pmu_init+0x1c/0x28
  |  arm_pmu_device_probe+0x1b4/0x558
  |  armv8_pmu_device_probe+0x18/0x20
  |  platform_probe+0x64/0xd0
  |  hw perfevents: enabled with armv8_cortex_a57 PMU driver, 7 counters available

Introduce a state variable to track creation of the sysctl file and
ensure that it is only created once.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Fixes: e201260081 ("arm64: perf: Add userspace counter access disable switch")
Link: https://lore.kernel.org/r/CAMuHMdVcDxR9sGzc5pcnORiotonERBgc6dsXZXMd6wTvLGA9iw@mail.gmail.com
Signed-off-by: Will Deacon <will@kernel.org>
2022-01-04 14:57:14 +00:00
..
boot arm64: dts: exynos: drop samsung,ufs-shareability-reg-offset in ExynosAutov9 2021-11-25 14:46:00 +01:00
configs ARM: defconfig updates for 5.16 2021-11-03 17:07:02 -07:00
crypto crypto: arm64/aes-ccm - avoid by-ref argument for ce_aes_ccm_auth_data 2021-09-17 11:05:11 +08:00
hyperv arm64: hyperv: Initialize hypervisor on boot 2021-08-04 16:54:36 +00:00
include arm64: uaccess: avoid blocking within critical sections 2021-11-24 09:16:26 +00:00
kernel arm64: perf: Don't register user access sysctl handler multiple times 2022-01-04 14:57:14 +00:00
kvm KVM: arm64: Cap KVM_CAP_NR_VCPUS by kvm_arm_default_max_vcpus() 2021-11-18 02:12:14 -05:00
lib Kbuild updates for v5.16 2021-11-08 09:15:45 -08:00
mm kasan: add kasan mode messages when kasan init 2021-11-11 09:34:35 -08:00
net arm64 updates for 5.16 2021-11-01 16:33:53 -07:00
tools Merge branch 'for-next/trbe-errata' into for-next/core 2021-10-29 12:25:33 +01:00
xen xen: allow pv-only hypercalls only with CONFIG_XEN_PV 2021-11-02 08:11:01 -05:00
Kbuild kbuild: use more subdir- for visiting subdirectories while cleaning 2021-10-24 13:49:46 +09:00
Kconfig Merge branch 'akpm' (patches from Andrew) 2021-11-06 14:08:17 -07:00
Kconfig.debug
Kconfig.platforms ARM: SoC drivers for 5.16 2021-11-03 17:00:52 -07:00
Makefile kbuild: use more subdir- for visiting subdirectories while cleaning 2021-10-24 13:49:46 +09:00