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Venkatesh Pallipadi 8a9e1b0f56 [PATCH] Platform SMIs and their interferance with tsc based delay calibration ... Issue: Current tsc based delay_calibration can result in significant errors in loops_per_jiffy count when the platform events like SMIs (System Management Interrupts that are non-maskable) are present. This could lead to potential kernel panic(). This issue is becoming more visible with 2.6 kernel (as default HZ is 1000) and on platforms with higher SMI handling latencies. During the boot time, SMIs are mostly used by BIOS (for things like legacy keyboard emulation). Description: The psuedocode for current delay calibration with tsc based delay looks like (0) Estimate a value for loops_per_jiffy (1) While (loops_per_jiffy estimate is accurate enough) (2) wait for jiffy transition (jiffy1) (3) Note down current tsc (tsc1) (4) loop until tsc becomes tsc1 + loops_per_jiffy (5) check whether jiffy changed since jiffy1 or not and refine loops_per_jiffy estimate Consider the following cases Case 1: If SMIs happen between (2) and (3) above, we can end up with a loops_per_jiffy value that is too low. This results in shorted delays and kernel can panic () during boot (Mostly at IOAPIC timer initialization timer_irq_works() as we don't have enough timer interrupts in a specified interval). Case 2: If SMIs happen between (3) and (4) above, then we can end up with a loops_per_jiffy value that is too high. And with current i386 code, too high lpj value (greater than 17M) can result in a overflow in delay.c:__const_udelay() again resulting in shorter delay and panic(). Solution: The patch below makes the calibration routine aware of asynchronous events like SMIs. We increase the delay calibration time and also identify any significant errors (greater than 12.5%) in the calibration and notify it to user. Patch below changes both i386 and x86-64 architectures to use this new and improved calibrate_delay_direct() routine. Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by: Adrian Bunk <bunk@stusta.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>		20 years ago
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alpha	…
arm	[PATCH] use ${CROSS_COMPILE}installkernel in arch/*/boot/install.sh	20 years ago
arm26	[PATCH] use ${CROSS_COMPILE}installkernel in arch/*/boot/install.sh	20 years ago
cris	[PATCH] make each arch use mm/Kconfig	20 years ago
frv	[PATCH] make each arch use mm/Kconfig	20 years ago
h8300	[PATCH] make each arch use mm/Kconfig	20 years ago
i386	[PATCH] Platform SMIs and their interferance with tsc based delay calibration	20 years ago
ia64	…
m32r	…
m68k	[PATCH] make each arch use mm/Kconfig	20 years ago
m68knommu	…
mips	[PATCH] mm/Kconfig: kill unused ARCH_FLATMEM_DISABLE	20 years ago
parisc	[PATCH] mm/Kconfig: kill unused ARCH_FLATMEM_DISABLE	20 years ago
ppc	[PATCH] make each arch use mm/Kconfig	20 years ago
ppc64	[PATCH] use ${CROSS_COMPILE}installkernel in arch/*/boot/install.sh	20 years ago
s390	[PATCH] use ${CROSS_COMPILE}installkernel in arch/*/boot/install.sh	20 years ago
sh	[PATCH] mm/Kconfig: kill unused ARCH_FLATMEM_DISABLE	20 years ago
sh64	…
sparc	…
sparc64	[PATCH] make each arch use mm/Kconfig	20 years ago
um	…
v850	…
x86_64	[PATCH] Platform SMIs and their interferance with tsc based delay calibration	20 years ago