deadlock | Python implementation of minilock.io , an encryption utility | File Sharing library

So is there any way to acquire those locks only if all of them are available?

No. Not with standard library mutex at least. There is no way to "check" if a lock is available, or "try" acquiring a lock. Every call of Lock() will block until locking is successful.

The implementation of mutex relies on atomic operations which only act on a single value at once. In order to achieve what you describe, you'd need some kind of "meta locking" where execution of the lock and unlock methods are themselves protected by a lock, but this probably isn't necessary just to have correct and safe locking in your program:

Penelope Stevens' comment explains correctly: As long as the order of acquisition is consistent between different goroutines, you won't get deadlocks, even for arbitrary subsets of the locks, if each goroutine eventually releases the locks it acquires.

If the structure of your program provides some obvious locking order, then use that. If not, you can create your own special mutex type that has intrinsic ordering.

This is simply because you are trying to have access to a field of a null struct (myproc()->pid).

As you may know, myproc() returns a process running on the current processor. If you look at main.c, you may notice that the bootstrap processor starts running there. Therefore, if we can find a function which calls the acquire() function before setting up the first process, the problem will be solved.

If you take a close look at the kinit1 function, you can realize that the acquire function is called in it. Consequently, we found a function that uses the acquire function, even before initializing the ptable struct. Therefore, when you try to access the myproc() value, it is not initialized yet.

Please elaborate your use case. If you two have threads trying to secure a lock you can simply fire the update statements simultaneously and based on row count returned from the update you can frame the logic accordingly. Need more information to be able to comment.

Looking at your code, two things can cause a deadlock:

• errg.Wait() blocks the execution of the main goroutine until all initialized goroutines are finished. However, each goroutine is blocked when trying to write to mapChan, because you never get to read from it (because it is below the errg.Wait()).
• You never read from sliceChan, so that is a potential deadlock right there.

Here is the link to the modified Playground code, but most of the changes are in the main function.

Yes, you can safely wait on a "compound predicate," where one signal means "this state changed or that state changed or some other state changed or ..."

In your case, those states are the event_v flags you set. Presuming your main thread is in a loop, and that the event_v flags are initialized to false, it'd look something like this:

This is literally the code that was so confusing that its original authors wrote "You are not expected to understand this" in the comments, so don't feel bad for not understanding it.

The key thing you may have missed is that p->context contains an address where swtch is to resume execution of process p. It's set up, for instance, here:

As you are using async method, probably you'll need some kind of await there

Like:

Instead of using two event handler for same task you can combine them . So ,whenever your toggle element gets clicked you can check if the .data('text') is Markdown or not depending on this you change your selector i.e : prev() or next()

Demo Code :

// What I want is for one thread to try to call methodB() while the other thread is in methodB() trying to call methodA().

That's not a deadlock. The thread that's trying to call methodB() simply will be forced to wait until the other thread releases the lock by returning from its methodB() call.

To get a classic deadlock, you need to have two locks. Your program has only one lock—the intrinsic lock belonging to the single instance of SharedObject that your program creates.

A classic deadlock is when one thread has already acquired lock A and is waiting to acquire lock B while the other thread has acquired lock B, and it's waiting to acquire lock A. In that case, neither thread can make progress until the other thread releases its lock. But, neither thread will release its lock because neither thread can make progress.

You need two locks. You have two methods (methodA() and methodB()), but they both lock the same lock.