Concurrency issues in reader-writer problem

[Hunk]

Hi

I would like some ideas on way to solve the concurrency issue. The
problem is , I have an object say X which multiple readers need to
access and also to update. They do so by say two functions :
// simplistic view of the problem
Read()
{
return X;
}

Update(Y)
{
X= Y;
}

Now I would like to block any reader while calling update. With the
general solutions provided of having say a mutex and using it in Read
and Update would solve the problem. But then this would block multiple
readers also which is not desired. i.e a block on read should be
allowed only when update is called. Having a boolean and checkin is
not ideal as the atomicity of the operation is not guaranteed. Any
ideas on this?

[dasjotre]

On 21 Feb, 11:08, "Hunk" <santosh.udyav. [e-mail] te:

Hi

I would like some ideas on way to solve the concurrency issue. The
problem is , I have an object say X which multiple readers need to
access and also to update. They do so by say two functions :
// simplistic view of the problem
Read()
{
return X;

}

Update(Y)
{
X= Y;

}

Now I would like to block any reader while calling update. With the
general solutions provided of having say a mutex and using it in Read
and Update would solve the problem. But then this would block multiple
readers also which is not desired. i.e a block on read should be
allowed only when update is called. Having a boolean and checkin is
not ideal as the atomicity of the operation is not guaranteed. Any
ideas on this?

you nead reader-writer lock. the best implementation I've
seen is Valery Pryamikov's mrsw_guard

[Bharath]

On Feb 21, 3:08 am, "Hunk" <santosh.udyav. [e-mail] te:

Hi

I would like some ideas on way to solve the concurrency issue. The
problem is , I have an object say X which multiple readers need to
access and also to update. They do so by say two functions :
// simplistic view of the problem
Read()
{
return X;

}

Update(Y)
{
X= Y;

}

Now I would like to block any reader while calling update. With the
general solutions provided of having say a mutex and using it in Read
and Update would solve the problem. But then this would block multiple
readers also which is not desired. i.e a block on read should be
allowed only when update is called. Having a boolean and checkin is
not ideal as the atomicity of the operation is not guaranteed. Any
ideas on this?

Is this a multi-threaded program? If it is, the best solution is to
use read-write locks in pthread library. See the manpage of
pthread_rwlock_ wrlock and pthread_rwlock_ rdlock. Note that you need to
have -DUSE_UNIX98 in your compiler flags.

[Hunk]

On Feb 21, 7:55 pm, "Bharath" <cbku...@gmail. comwrote:

On Feb 21, 3:08 am, "Hunk" <santosh.udyav. [e-mail] te:

Hi

I would like some ideas on way to solve the concurrency issue. The
problem is , I have an object say X which multiple readers need to
access and also to update. They do so by say two functions :
// simplistic view of the problem
Read()
{
return X;

}

Update(Y)
{
X= Y;

}

Now I would like to block any reader while calling update. With the
general solutions provided of having say a mutex and using it in Read
and Update would solve the problem. But then this would block multiple
readers also which is not desired. i.e a block on read should be
allowed only when update is called. Having a boolean and checkin is
not ideal as the atomicity of the operation is not guaranteed. Any
ideas on this?

Is this a multi-threaded program? If it is, the best solution is to
use read-write locks in pthread library. See the manpage of
pthread_rwlock_ wrlock and pthread_rwlock_ rdlock. Note that you need to
have -DUSE_UNIX98 in your compiler flags.- Hide quoted text -

- Show quoted text -

Thanks... yes it is a multithreaded program. i'll take a look at the
reader writer locks mentioned. Any idea on how this is implemented in
zthreads?

[Bharath]

On Feb 21, 9:59 pm, "Hunk" <santosh.udyav. [e-mail] te:

On Feb 21, 7:55 pm, "Bharath" <cbku...@gmail. comwrote:

On Feb 21, 3:08 am, "Hunk" <santosh.udyav. [e-mail] te:

Hi

I would like some ideas on way to solve the concurrency issue. The
problem is , I have an object say X which multiple readers need to
access and also to update. They do so by say two functions :
// simplistic view of the problem
Read()
{
return X;

}

Update(Y)
{
X= Y;

}

Now I would like to block any reader while calling update. With the
general solutions provided of having say a mutex and using it in Read
and Update would solve the problem. But then this would block multiple
readers also which is not desired. i.e a block on read should be
allowed only when update is called. Having a boolean and checkin is
not ideal as the atomicity of the operation is not guaranteed. Any
ideas on this?

Is this a multi-threaded program? If it is, the best solution is to
use read-write locks in pthread library. See the manpage of
pthread_rwlock_ wrlock and pthread_rwlock_ rdlock. Note that you need to
have -DUSE_UNIX98 in your compiler flags.- Hide quoted text -

- Show quoted text -

Thanks... yes it is a multithreaded program. i'll take a look at the
reader writer locks mentioned. Any idea on how this is implemented in
zthreads?- Hide quoted text -

- Show quoted text -

I never used zthreads but this link might help.
http://zthread.sourceforge.net/html/...WriteLock.html

[Chris Thomasson]

"dasjotre" <da******@googl email.comwrote in message
news:11******** **************@ q2g2000cwa.goog legroups.com...

On 21 Feb, 11:08, "Hunk" <santosh.udyav. [e-mail] te:

[...]

you nead reader-writer lock. the best implementation I've
seen is Valery Pryamikov's mrsw_guard

how does it compare to the following algorithm:

[Chris Thomasson]

DOH! sorry for the other msg... I left out the link!

"dasjotre" <da******@googl email.comwrote in message
news:11******** **************@ q2g2000cwa.goog legroups.com...

On 21 Feb, 11:08, "Hunk" <santosh.udyav. [e-mail] te:

[...]

you nead reader-writer lock. the best implementation I've
seen is Valery Pryamikov's mrsw_guard

how does it compare to the following algorithm:

http://groups.google.com/group/comp....fb0ed46a4bcb4b

[Chris Thomasson]

"Hunk" <sa************ **@gmail.comwro te in message
news:11******** *************@t 69g2000cwt.goog legroups.com...

Hi

I would like some ideas on way to solve the concurrency issue.

Sure:

http://groups.google.com/group/comp....6ad37c34dd673a

http://groups.google.com/group/comp....fb0ed46a4bcb4b

http://appcore.home.comcast.net/
How about we transfer this thread over to comp.programmin g.threads before we
go any further?

[Chris Thomasson]

A while back I was thinking about fully integrating a working solution to
the reader-writer problem directly into the C++ STL:

http://groups.google.com/group/comp....c9c2673682d4cf

[Chris Thomasson]

"Chris Thomasson" <cr*****@comcas t.netwrote in message
news:PZ******** *************** *******@comcast .com...

DOH! sorry for the other msg... I left out the link!

"dasjotre" <da******@googl email.comwrote in message
news:11******** **************@ q2g2000cwa.goog legroups.com...

>On 21 Feb, 11:08, "Hunk" <santosh.udyav. [e-mail] te:

[...]

>you nead reader-writer lock. the best implementation I've
seen is Valery Pryamikov's mrsw_guard

how does it compare to the following algorithm:

http://groups.google.com/group/comp....fb0ed46a4bcb4b

Or this rw-spinlock implementation:

http://appcore.home.comcast.net/appc...k_algo1_c.html

http://appcore.home.comcast.net/appc...k_algo1_h.html