Issue with lock(this) { ... }

[Max Adams]

All,

I have a multithreaded app (using threadpool). I was under the illusion
that where I used lock( this ) around a segment of code that only one thread
would be allowed access to that segment of code at a time.

The scenario I have is that a part of code creates a document "new.txt" (for
simplicity) and zips it up, I only ever want one "new.txt" so I put this
code inside a lock( this ), however having reviewed my code this does not
act as desired; I see many threads inside this locked section at the same
time :-/

Am I missing something?

MA

[Jon Skeet [C# MVP]]

Max Adams <ru************@hotmail.com> wrote:

I have a multithreaded app (using threadpool). I was under the illusion
that where I used lock( this ) around a segment of code that only one thread
would be allowed access to that segment of code at a time.
For that one instance, yes.
The scenario I have is that a part of code creates a document "new.txt" (for
simplicity) and zips it up, I only ever want one "new.txt" so I put this
code inside a lock( this ), however having reviewed my code this does not
act as desired; I see many threads inside this locked section at the same
time :-/

Am I missing something?

Could you post a short but complete program which demonstrates the
problem?

See http://www.pobox.com/~skeet/csharp/complete.html for details of
what I mean by that.

Also, have a look at

http://www.pobox.com/~skeet/csharp/threads/
and in particular
http://www.pobox.com/~skeet/csharp/t...ckchoice.shtml

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,

It's not a good idea to use lock( this ), as it block the entire instance,
create one instance member and lock it,

take a look at:
http://www.yoda.arachsys.com/csharp/.../locking.shtml

cheers,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation

"Max Adams" <ru************@hotmail.com> wrote in message
news:O9**************@TK2MSFTNGP15.phx.gbl...

All,

I have a multithreaded app (using threadpool). I was under the illusion
that where I used lock( this ) around a segment of code that only one thread would be allowed access to that segment of code at a time.

The scenario I have is that a part of code creates a document "new.txt" (for simplicity) and zips it up, I only ever want one "new.txt" so I put this
code inside a lock( this ), however having reviewed my code this does not
act as desired; I see many threads inside this locked section at the same
time :-/

Am I missing something?

MA

[Scott Allen]

Blocking across the entire instance is often the desired effect, I
think the real concern of lock(this) is code outside of the class can
also lock on the object reference, which can cause problems.

--
Scott
http://www.OdeToCode.com/blogs/scott/

On Thu, 21 Oct 2004 11:16:40 -0400, "Ignacio Machin \( .NET/ C# MVP
\)" <ignacio.machin AT dot.state.fl.us> wrote:

Hi,

It's not a good idea to use lock( this ), as it block the entire instance,
create one instance member and lock it,

take a look at:
http://www.yoda.arachsys.com/csharp/.../locking.shtml

cheers,

[Richard Blewett [DevelopMentor]]

And besides, lock(this) *doesn't* block across the entire instance. It simply blocks other callers of lock(this) (or external objects that decide to synchronize of that particular instance).

I could theoretcally use lock(this) to only protect one field in my object.

Regards

Richard Blewett - DevelopMentor
http://staff.develop.com/richardb/weblog

nntp://news.microsoft.com/microsoft.public.dotnet.languages.csharp/<2h********************************@4ax.com>

Blocking across the entire instance is often the desired effect, I
think the real concern of lock(this) is code outside of the class can
also lock on the object reference, which can cause problems.