What is the difference between spinlockirqsave() and spinlockirq()?
What is the difference between spinlockirqsave() and spinlockirq()?
spin_lock_irqsave is basically used to save the interrupt state before taking the spin lock, this is because spin lock disables the interrupt, when the lock is taken in interrupt context, and re-enables it when while unlocking. The interrupt state is saved so that it should reinstate the interrupts again.
What is Spin_lock_bh?
spin_lock_bh prevents a softirq running on the same CPU as the caller while the lock is held. Since the userspace process can be preempted by a softirq, this prevents a deadlock from occurring if a softirq waits for a spin-lock that is already locked by the same CPU.
Can spinlock Rwlock be used in interrupt handler?
The answer is yes and no. you can use the up and unlock, but you can’t use down and lock, as these are blocking calls which put the process to sleep and we are not supposed to sleep in interrupt handlers.
What is spin lock in Linux?
The basic form of locking in the Linux kernel is the spinlock. Spinlocks take their name from the fact that they continuously loop, or spin, waiting to acquire a lock. This section of code sets the spin_lock to “unlocked,” or 0, on line 66 and initializes the other variables in the structure.
Can interrupts be preempted?
2 Answers. Simple answer: An interrupt can only be interrupted by interrupts of higher priority. Therefore an interrupt can be interrupted by the kernel or a user task if the interrupt’s priority is lower than the kernel scheduler interrupt priority or user task interrupt priority.
What is interrupt lock?
The InterruptLock() function guards a critical section by locking the specified spinlock. You can call this function from a thread or from an interrupt handler. This function tries to acquire the spinlock (a variable shared between the interrupt handler and a thread) while interrupts are disabled.
What is soft IRQ?
SoftIrqs allow the critical part of servicing hardware interrupts to be as short as possible; instead of having to process the entire hw interrupt on the spot, the important data is read off the device into RAM or otherwise, and then a SoftIrq is started to finish the work.
How does a spinlock work?
Spin locks are a low-level synchronization mechanism suitable primarily for use on shared memory multiprocessors. When the calling thread requests a spin lock that is already held by another thread, the second thread spins in a loop to test if the lock has become available.
Can I lock a spinlock in one CPU and unlock it another CPU?
Using spinlocks on a single-core/single-CPU system makes usually no sense, since as long as the spinlock polling is blocking the only available CPU core, no other thread can run and since no other thread can run, the lock won’t be unlocked either.
How do you initialize a spinlock?
The Spinlock can be initialized via “DEFINE_SPINLOCK” MACRO or by invoking the “spin_lock_init” MACRO. The “DEFINE_SPINLOCK” MACRO is usually used when the spinlock is statically assigned.
What is preemptive blocking?
Preemptive blocking, What is preemptive blocking. This is done by noting any danger signs of impending threats and then. blocking the user or IP address from which these signs originate. here is the potential of blocking a legitimate user by mistake.