8451a86f0a
- When the cpu halts, the interrupts are enable so the cpu may be woken up. When the interrupt handler returns but another interrupt is available it is also serviced immediately. This is not a problem per-se. It only slightly breaks time accounting as idle accounted is for the kernel time in the interrupt handler. - As the big kernel lock is lock/unlocked in the smp branch in the time acounting functions as they are called exactly at the places we need to take the lock) this leads to a deadlock. - we make sure that once the interrupt handler returns from the nested trap, the interrupts are disabled. This means that only one interrupt is serviced after idle is interrupted. - this requires the loop in apic timer calibration to keep reenabling the interrupts. I admit it is a little bit hackish (one line), however, this code is a stupid corner case at the boot time. Hopefully it does not matter too much. |
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i386 |