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| author |   Will Deacon <will@kernel.org> | 2022-01-04 14:57:14 +0000 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2022-01-04 14:57:14 +0000 |
| commit | 3da4390bcdf4dcea5eb7961f1ba05f75c642a39d (patch) | |
| tree | 3cff9c60e085839ab933bcf58a10e7dfc2684739 | |
| parent | drivers: perf: marvell_cn10k: fix an IS_ERR() vs NULL check (diff) | |
| download | linux-dev-3da4390bcdf4dcea5eb7961f1ba05f75c642a39d.tar.xz linux-dev-3da4390bcdf4dcea5eb7961f1ba05f75c642a39d.zip | |
arm64: perf: Don't register user access sysctl handler multiple times
Commit e2012600810c ("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: e2012600810c ("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>
| -rw-r--r-- | arch/arm64/kernel/perf_event.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c index 4c5c8d731fbb..cab678ed6618 100644 --- a/arch/arm64/kernel/perf_event.c +++ b/arch/arm64/kernel/perf_event.c @@ -1214,6 +1214,14 @@ static struct ctl_table armv8_pmu_sysctl_table[] = { { } }; +static void armv8_pmu_register_sysctl_table(void) +{ + static u32 tbl_registered = 0; + + if (!cmpxchg_relaxed(&tbl_registered, 0, 1)) + register_sysctl("kernel", armv8_pmu_sysctl_table); +} + static int armv8_pmu_init(struct arm_pmu *cpu_pmu, char *name, int (*map_event)(struct perf_event *event), const struct attribute_group *events, @@ -1248,8 +1256,7 @@ static int armv8_pmu_init(struct arm_pmu *cpu_pmu, char *name, cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_CAPS] = caps ? caps : &armv8_pmuv3_caps_attr_group; - register_sysctl("kernel", armv8_pmu_sysctl_table); - + armv8_pmu_register_sysctl_table(); return 0; } |