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Why can't a process disable the interrupts to avoid context switch while in the critical section to avoid the race condition?
Wiki User
∙ 11y ago
Because only the operating system has that authority.
Wiki User
∙ 11y ago
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Why Disable all interrupts was allowed in kernel mode?
It usually doesn't. You may think of one of the followings: 1. When processing a higher priority interrupt, more interrupts with lower priority are not allowed. 2. During the context-switch (user-mode<->kernel-mode, entering/exiting interrupt/exception handler), interrupts may be disabled. 3. When in a critical operation (eg. manipulating shared data), interrupts may have to be disabled (for a very short time-interval).
What is EI and DI instructions?
The Enable Interrupts (EI) and Disable Interrupts (DI) instructions allow the MP to permit or deny interrupts under program control.
Why there is a need for disabling interrupts in 8085?
Interrupt are automatically disabled on interrupt entry (except for TRAP, which is non-maskable) so that interrupts do not, by default, nest. You would also disable enterrupts surrounding a critical section of code that, perhaps, manipulated an interrupt register. It is possible to re-enable interrupts during an interrupt service routine. Typically, you would have a hierarchy, such as RST7.5, then RST 6.5, then RST 5.5. Initially, at interrupt entry, all interrupts are disabled. You could then manipulate the interrupt mask using the RIM and SIM instructions and enable further interrupts, allowing a nested architecture. At interrupt exit, then, you would disable interrupts, reset the mask, enable interrupts, and return from interrupt.
Explain why implementing synchronization primitives by disabling interrupts is not appropriate in a single-processor system if the synchronization primitives are to be used in user-level programs?
Interrupts are not sufficient in multiprocessor systems since disabling inter rupts only prevents other processes from executing on the processor in which inter rupts were disabled; there are no limitations on what processes could be executing on other processors and therefore the process disabling interrupts cannot guarantee mutually exclusive access to program state.
How can mask or unmask the interrupts in 8085?
DI = Disable all interrupts (except TRAP) EI = Enable all interrupts Also, SIM can selectively mask RST5.5, RST6.5, and RST7.5.
Shared data problem in embedded system?
if a variable is used by multiple tasks or processes, conflict arises.the variable value will become inconsistent. solutions are to disable interrupts when critical region starts execution, using semaphores.
Which register is used to set priority for interrupts?
The 8085 does not have an adjustable priority interrupt schema. You can only turn interrupts off, and mask certain interrupts, such as RST5.5, RST6.5, and RST7.5. However, that said, you can implement a priority schema, of sorts, within these interrupts, including INTR, by using the SIM instruction. You can't change the basic priority but you can disable certain interrupts while others are being serviced, if you so choose.
What is maskable in Intel 8085 microprocessore?
Four of the interrupts in the Intel 8085 (INTR, RST5.5, RST6.5, and RST7.5) are maskable, while one interrupt (TRAP) is non-maskable.The eight RSTx type of software "interrupts" are not really interrupts, but if they were treated as interrupts, they would be non-maskable.
Q2 What would be the effect of disabling interrupts in hardware based synchronization in terms of critical interrupts like system clock?
If you disable a maskable interrupt that has any kind of important timing function, such as a system clock, by more than the allowable tolerance for that function, then your system is not going to function correctly. Your system design must consider that certain functions must be able to be processed in a certain time. If you cannot do this, you either need to redesign/reorganize your processing routine(s), you need to change the requirements of your system, or you need to get a faster processor. Sometimes you can disable interrupts for a short period of time and delay the processing of new interrupts, so long as no interrupts are missed, and so long as the end result is that the required functionality is met. Processing bytes from a UART, for instance, could be delayed so long as the average throughput was maintained and so long as the UART's internal FIFO does not overflow. This is just an example. Each case is evaluated on its own merits.
Why i can't enable and disable interrupts of my AVR for several times?
It's impossible :o) You can disable and enable any interrupt source by setting or clearing corresponding bit in proper control register. Show me your code - we will see what can be done wrong. Asar fotousa@interia.pl You can set bit I on SREG by 1 to enable global interrupt or by 0 to disable it. in c programming you can write #asm ("sei") //to enable global interupt #asm ("cli") //to disable global interupt M. Wicaksono A.
What is the meaning of maskable hardware interrupt?
A maskable hardware interrupt is one that can be disabled, or masked, by instructions in the CPU. In the 8085, all interupts except TRAP and (software) RST N can be masked by disabling interrupts, and RST7.5, RST6.5, and RST5.5 can be individually masked with the SIM (Set Interrupt Mask) instruction. In general, you leave interrupts disabled until one instruction before returning. In the case of the RST*.5 interrupts, you can mask it during interrupt processing and then enable interrupts, allowing other levels to interrupt you again. At the conclusion of the interrupt routine, you would disable interrupts, restore the mask, enable interrupts, and return. If you use this method, you can choose the nesting priority as desired. You determine what mask to set using the RIM (Read Interrupt Mask) instruction and then do bit manipulation before using SIM.
What is an interrupt and how are multiple interrupts dealt with?
An Interrupt is a signal that goes into a microprocessor that tells it something has happened that needs attention. There are generally dedicated pins on the microprocessor, often called "Int" (for Interrupt) and "NMI" (for Non-Maskable Interrupt). For a microprocessor, an interrupt signal is like the bell on a telephone is for you; it's a notice that you should stop what you are doing now and deal with this issue that has come up. Exact procedures for dealing with an interrupt vary from one microprocessor to another; generally, the microprocessor puts out a signal that says "Where should I go, then?" and a piece of hardware, the Interrupt Controller, then responds with a signal that tells it which condition has happened. The processor then starts processing the indicated piece of code, and that piece of code handles the condition. The Interrupt Controller often handles setting priority for interrupts, accepting a number of signals (often four), and setting priorities on each. It will trigger another interrupt in the middle of processing one if the new interrupt is a higher priority than the one that is already being processed, or will hold on to the lower priority one until the CPU is finished with a higher-priority one. The CPU can often "disable interrupts" when it is doing something time-critical. At such times, the only interrupt that can occur is the Non-Maskable Interrupt, which is generally reserved for critical error conditions that have to be dealt with immediately no matter what else is going on.
