Multi-core Mutex
Posted: Tue Oct 23, 2012 11:52 am
Hello everyone,
I just thought about the fact that when a program within an OS, on a multi-core CPU, is requesting an mutex (e.g. for writing to HDD) this could possibly leak.
For example, this is how the mutex gets requested (pseudocode):
It could leak when the following happens (they are both requesting the same mutex):
As you can see, if both CPU cores are requesting the same mutex (flag in memory) at the same time, what is quite unlikely but definitely possible, they are both continuing like they have the mutex, which could result in serious problems for the OS.
Now I was wondering how this is being solved in nowadays OS's, or how you should solve this.
Thanks,
Dennis
I just thought about the fact that when a program within an OS, on a multi-core CPU, is requesting an mutex (e.g. for writing to HDD) this could possibly leak.
For example, this is how the mutex gets requested (pseudocode):
Code: Select all
m = getCurrentMutexState();
if( isNotUsed( m ) ){
setMutexUsed( m );
/* code here */
setMutexUnused( m );
}
tryAgain();Code: Select all
CORE1: core1m=getCurrentMutexState(); // not in use
CORE2: core2m=getCurrentMutexState(); // not in use
CORE1: if( isNotUsed(core1m) ) // not in use, so continue
CORE2: if( isNotUsed(core2m) ) // still not set as used
CORE1: setMutexUsed( core1m ) // now it is in use
CORE2: setMutexUsed( core2m ) // it was in use, still in use
etc.Now I was wondering how this is being solved in nowadays OS's, or how you should solve this.
Thanks,
Dennis