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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2017-11-13 02:15:39 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2017-11-13 19:42:39 -0800
commitb29c6ef7bb1257853c1e31616d84f55e561cf631 (patch)
treedd055a870644df922f4274fdd093b37240268f4f /kernel
parent99306dfc067e6098365d395168b6fd5db3095292 (diff)
download96b-common-b29c6ef7bb1257853c1e31616d84f55e561cf631.tar.gz
x86 / CPU: Avoid unnecessary IPIs in arch_freq_get_on_cpu()
Even though aperfmperf_snapshot_khz() caches the samples.khz value to return if called again in a sufficiently short time, its caller, arch_freq_get_on_cpu(), still uses smp_call_function_single() to run it which may allow user space to trigger an IPI storm by reading from the scaling_cur_freq cpufreq sysfs file in a tight loop. To avoid that, move the decision on whether or not to return the cached samples.khz value to arch_freq_get_on_cpu(). This change was part of commit 941f5f0f6ef5 ("x86: CPU: Fix up "cpu MHz" in /proc/cpuinfo"), but it was not the reason for the revert and it remains applicable. Fixes: 4815d3c56d1e (cpufreq: x86: Make scaling_cur_freq behave more as expected) Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Reviewed-by: WANG Chao <chao.wang@ucloud.cn> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
0 files changed, 0 insertions, 0 deletions