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| author |  Uros Bizjak <ubizjak@gmail.com>
| 2023-11-23 21:34:23 +0100 |
|---|---|---|
| committer |  Ingo Molnar <mingo@kernel.org>
| 2023-11-30 20:25:09 +0100 |
| commit | 9e9d673b2c84719937db5d6ab1d8cbcd7d45e974 (patch) | |
| tree | a258dea9e23cb10d51a214f04b4d03ef019aa0dc /arch/x86/kernel/smp.c | |
| parent | x86/smp: Move the call to smp_processor_id() after the early exit in native_s... (diff) | |
| download | linux-9e9d673b2c84719937db5d6ab1d8cbcd7d45e974.tar.gz linux-9e9d673b2c84719937db5d6ab1d8cbcd7d45e974.tar.bz2 linux-9e9d673b2c84719937db5d6ab1d8cbcd7d45e974.zip | |
x86/smp: Use atomic_try_cmpxchg in native_stop_other_cpus()
Use atomic_try_cmpxchg() instead of atomic_cmpxchg(*ptr, old, new) == old.
X86 CMPXCHG instruction returns success in ZF flag, so this change saves a
compare after the CMPXCHG.
Tested by building a native Fedora-38 kernel and rebooting
a 12-way SMP system using "shutdown -r" command some 100 times.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231123203605.3474745-2-ubizjak@gmail.com
Diffstat (limited to 'arch/x86/kernel/smp.c')
| -rw-r--r-- | arch/x86/kernel/smp.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c index 65dd44e3fc1c..1bb79526c217 100644 --- a/arch/x86/kernel/smp.c +++ b/arch/x86/kernel/smp.c @@ -148,15 +148,16 @@ static int register_stop_handler(void) static void native_stop_other_cpus(int wait) { - unsigned int this_cpu; + unsigned int old_cpu, this_cpu; unsigned long flags, timeout; if (reboot_force) return; /* Only proceed if this is the first CPU to reach this code */ + old_cpu = -1; this_cpu = smp_processor_id(); - if (atomic_cmpxchg(&stopping_cpu, -1, this_cpu) != -1) + if (!atomic_try_cmpxchg(&stopping_cpu, &old_cpu, this_cpu)) return; /* For kexec, ensure that offline CPUs are out of MWAIT and in HLT */ |