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| author | Thomas Gleixner <tglx@linutronix.de> | 2023-05-12 23:07:17 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2023-05-15 13:44:53 +0200 |
| commit | 9d349d47f0e39b4d1b68793ded2459daa1f948f0 (patch) | |
| tree | d3f00d8c37867b3b98609ce9402cb87f29a8ab68 /arch/x86/kernel/smpboot.c | |
| parent | d4f28f07c2fe736bce8ca415a86fb74c629200f3 (diff) | |
| download | linux-9d349d47f0e39b4d1b68793ded2459daa1f948f0.tar.gz linux-9d349d47f0e39b4d1b68793ded2459daa1f948f0.tar.bz2 linux-9d349d47f0e39b4d1b68793ded2459daa1f948f0.zip | |
x86/smpboot: Make TSC synchronization function call based
Spin-waiting on the control CPU until the AP reaches the TSC
synchronization is just a waste especially in the case that there is no
synchronization required.
As the synchronization has to run with interrupts disabled the control CPU
part can just be done from a SMP function call. The upcoming AP issues that
call async only in the case that synchronization is required.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> # Steam Deck
Link: https://lore.kernel.org/r/20230512205256.148255496@linutronix.de
Diffstat (limited to 'arch/x86/kernel/smpboot.c')
| -rw-r--r-- | arch/x86/kernel/smpboot.c | 20 |
1 files changed, 3 insertions, 17 deletions
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 8b07c6e6d620..b2f44a837ce1 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -275,11 +275,7 @@ static void notrace start_secondary(void *unused) */ smp_callin(); - /* - * Check TSC synchronization with the control CPU, which will do - * its part of this from wait_cpu_online(), making it an implicit - * synchronization point. - */ + /* Check TSC synchronization with the control CPU. */ check_tsc_sync_target(); /* @@ -1141,21 +1137,11 @@ static void wait_cpu_callin(unsigned int cpu) } /* - * Bringup step four: Synchronize the TSC and wait for the target AP - * to reach set_cpu_online() in start_secondary(). + * Bringup step four: Wait for the target AP to reach set_cpu_online() in + * start_secondary(). */ static void wait_cpu_online(unsigned int cpu) { - unsigned long flags; - - /* - * Check TSC synchronization with the AP (keep irqs disabled - * while doing so): - */ - local_irq_save(flags); - check_tsc_sync_source(cpu); - local_irq_restore(flags); - /* * Wait for the AP to mark itself online, so the core caller * can drop sparse_irq_lock. |