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| author |   Paul E. McKenney <paulmck@kernel.org> | 2020-09-03 15:23:29 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-11-06 16:59:11 -0800 |
| commit | 3fcd6a230fa7d03bffcb831a81b40435c146c12b (patch) | |
| tree | bc576b40954c9deb95bf32151cb4535fe889297f /kernel/rcu | |
| parent | x86/cpu: Avoid cpuinfo-induced IPI pileups (diff) | |
| download | linux-dev-3fcd6a230fa7d03bffcb831a81b40435c146c12b.tar.xz linux-dev-3fcd6a230fa7d03bffcb831a81b40435c146c12b.zip | |
x86/cpu: Avoid cpuinfo-induced IPIing of idle CPUs
Currently, accessing /proc/cpuinfo sends IPIs to idle CPUs in order to
learn their clock frequency. Which is a bit strange, given that waking
them from idle likely significantly changes their clock frequency.
This commit therefore avoids sending /proc/cpuinfo-induced IPIs to
idle CPUs.
[ paulmck: Also check for idle in arch_freq_prepare_all(). ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: <x86@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 06895ef85d69..1d84c0b6a9f3 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -341,6 +341,14 @@ static bool rcu_dynticks_in_eqs(int snap) return !(snap & RCU_DYNTICK_CTRL_CTR); } +/* Return true if the specified CPU is currently idle from an RCU viewpoint. */ +bool rcu_is_idle_cpu(int cpu) +{ + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); + + return rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp)); +} + /* * Return true if the CPU corresponding to the specified rcu_data * structure has spent some time in an extended quiescent state since |