Doug / smarc-fsl-linux-kernel

Download as
Browse Code ยป

Commit ac619f4eba45da10053fc991f8a5d47b3be79fa3

Authored by Jan Beulich
Committed by Ingo Molnar
1 parent 7e794cb7e3
Exists in master and in 6 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

x86: Serialize SMP bootup CMOS accesses on rtc_lock 

With CPU hotplug, there is a theoretical race between other CMOS
(namely RTC) accesses and those done in the SMP secondary
processor bringup path.

I am unware of the problem having been noticed by anyone in practice,
but it would very likely be rather spurious and very hard to reproduce.
So to be on the safe side, acquire rtc_lock around those accesses.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/4E257AE7020000780004E2FF@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Showing 1 changed file with 8 additions and 0 deletions Side-by-side Diff

arch/x86/include/asm/smpboot_hooks.h
Diff comments   View file @ ac619f4
... ... @@ -10,7 +10,11 @@
10 10  
11 11 static inline void smpboot_setup_warm_reset_vector(unsigned long start_eip)
12 12 {
  13 + unsigned long flags;
  14 +
  15 + spin_lock_irqsave(&rtc_lock, flags);
13 16 CMOS_WRITE(0xa, 0xf);
  17 + spin_unlock_irqrestore(&rtc_lock, flags);
14 18 local_flush_tlb();
15 19 pr_debug("1.\n");
16 20 *((volatile unsigned short *)phys_to_virt(apic->trampoline_phys_high)) =
... ... @@ -23,6 +27,8 @@
23 27  
24 28 static inline void smpboot_restore_warm_reset_vector(void)
25 29 {
  30 + unsigned long flags;
  31 +
26 32 /*
27 33 * Install writable page 0 entry to set BIOS data area.
28 34 */
29 35  
... ... @@ -32,7 +38,9 @@
32 38 * Paranoid: Set warm reset code and vector here back
33 39 * to default values.
34 40 */
  41 + spin_lock_irqsave(&rtc_lock, flags);
35 42 CMOS_WRITE(0, 0xf);
  43 + spin_unlock_irqrestore(&rtc_lock, flags);
36 44  
37 45 *((volatile u32 *)phys_to_virt(apic->trampoline_phys_low)) = 0;
38 46 }