From 5c0927e10889a18497faf7a76aa390e39ddf6993 Mon Sep 17 00:00:00 2001 From: Tomas Hruby Date: Thu, 26 Jan 2012 11:39:40 +0000 Subject: [PATCH] SMP - clock calibration spurious IRQ deadlock fix - this patch fixes a deadlock which may occur if we get a spurious interrupt while calibrating clocks during the boot time. Since we never handle interrupts while in the kernel (BKL locked) the interrupt code locks the lock. This is a different situation, a corner case, boot time only. We do not return to userspace but to the kernel, so the BKL is not unlocked. So we need irq handler which leaves the BKL unlocked. The clock handler does it already, this patch adds a dummy spurious irq handler for the same reason. It is better to handle the situation this way to keep the normal runtime code simple. --- common/include/arch/i386/interrupt.h | 1 + kernel/arch/i386/apic.c | 20 +++++++++++++++++++- 2 files changed, 20 insertions(+), 1 deletion(-) diff --git a/common/include/arch/i386/interrupt.h b/common/include/arch/i386/interrupt.h index 86b9447ff..c13a1e422 100644 --- a/common/include/arch/i386/interrupt.h +++ b/common/include/arch/i386/interrupt.h @@ -49,6 +49,7 @@ #define XT_WINI_IRQ 5 /* xt winchester */ #define FLOPPY_IRQ 6 /* floppy disk */ #define PRINTER_IRQ 7 +#define SPURIOUS_IRQ 7 #define CMOS_CLOCK_IRQ 8 #define KBD_AUX_IRQ 12 /* AUX (PS/2 mouse) port in kbd controller */ #define AT_WINI_0_IRQ 14 /* at winchester controller 0 */ diff --git a/kernel/arch/i386/apic.c b/kernel/arch/i386/apic.c index b73b98f1a..05602da62 100644 --- a/kernel/arch/i386/apic.c +++ b/kernel/arch/i386/apic.c @@ -428,13 +428,22 @@ PRIVATE int calib_clk_handler(irq_hook_t * UNUSED(hook)) return 1; } +PRIVATE int spurious_irq_handler(irq_hook_t * UNUSED(hook)) +{ + /* + * Do nothing, only unlock the kernel so we do not deadlock! + */ + BKL_UNLOCK(); + return 1; +} + PRIVATE void apic_calibrate_clocks(unsigned cpu) { u32_t lvtt, val, lapic_delta; u64_t tsc_delta; u64_t cpu_freq; - irq_hook_t calib_clk; + irq_hook_t calib_clk, spurious_irq; BOOT_VERBOSE(printf("Calibrating clock\n")); /* @@ -467,6 +476,14 @@ PRIVATE void apic_calibrate_clocks(unsigned cpu) /* set the probe, we use the legacy timer, IRQ 0 */ put_irq_handler(&calib_clk, CLOCK_IRQ, calib_clk_handler); + /* + * A spurious interrupt may occur during the clock calibration. Since we + * do this calibration in kernel, we need a special handler which will + * leave the BKL unlocked like the clock handler. This is a corner case, + * boot time only situation + */ + put_irq_handler(&spurious_irq, SPURIOUS_IRQ, spurious_irq_handler); + /* set the PIC timer to get some time */ init_8253A_timer(system_hz); @@ -489,6 +506,7 @@ PRIVATE void apic_calibrate_clocks(unsigned cpu) /* remove the probe */ rm_irq_handler(&calib_clk); + rm_irq_handler(&spurious_irq); lapic_delta = lapic_tctr0 - lapic_tctr1; tsc_delta = sub64(tsc1, tsc0); -- 2.44.0