Subj : Re: recursive mutexes
To   : comp.programming.threads,comp.unix.programmer
From : David Schwartz
Date : Sun May 15 2005 04:13 am


"Uenal Mutlu" <520001085531-0001@t-online.de> wrote in message 
news:d66ogb$2fe$00$1@news.t-online.com...

> C and E are redundant, however application code (the current thread)
> cannot always know that it alread has the lock, though it could test for 
> it.

    Yes, it can and must know that it already has the lock. A function that 
operates on X should be defined as being called with X locked, or with X 
unlocked. It could even take a boolean that indicates whether the caller has 
locked the object or not, though this is rarely the right thing to do.

    Simply put, the only thing recursive mutexes gives you is the ability to 
write code that deals with X that can be called whether or not X is locked. 
This is not only almost never useful, but it's almost always dangerous.

    DS

.