Implementing "critical sections" using recursive mutex locks

Greetings.
I have chosen pthread mutexes for implementing critical sections in my ported Windows code. As you probably all know, mutexes do not by default support recursive locking and will deadlock if attempted. With Solaris 7 came support for recursive locking through the PTHREAD_MUTEX_RECURSIVE type of mutex. The problem I have encountered when using these recursive mutexes doesn't even involve recursive locking, yet only manifests itself when using the recursive type.
To pin-point the problem, I have written a very simple application that creates 10 threads and pauses (via sleep()) for an amount of time sufficient for all threads to complete. In each thread, a global mutex (recursive type) is locked and then immediately unlocked, with status going to stdout via printf. There is no problem with this simple application and all threads run to completion after each gets the mutex lock in succession. To really test the mutex however, I simulated a pre-empted or otherwise blocked thread via a call to sched_yield() after locking the mutex and before unlocking it. In this version of the application, only the first thread to acquire the mutex lock completes (after successfully locking and unlocking the mutex), and all other threads hang waiting to acquire the mutex lock.
Any insight on this problem or suspected problems with the code I described would be GREATLY appreciated! I would be happy to send the source to this simple application to anyone interested in observing it's behavior.
Regards and thanks in advance.
Chad Attermann
telic.net

Solaris 7 is shipped broken for recursive mutexes... You can fix it by using patch 106980-13 and everything it depends on...
Good luck!

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Should I be able to see a priority change using a mutex lock ?

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Is there any known issue about mutex lock used in JNI on Solaris 10?

Dear Oracle,
I'm facing a strange behavior when running a JNI application that use the mutex lock. The application hanged after running for a while on one of our Solaris 10 machines. After investigating the stack trace of the application, it shows that one of all the application's threads that access the JNI hold the mutex lock forever, and that cause the other threads cannot access the JNI. The same application works fine on other Solaris 10 machines.
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mutex_lock(&mutex)
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The Kernel version is SunOS 5.10 Generic_142900-14
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Best regards,
Krit K.

876587 wrote:
... and that cause the other threads cannot access the JNI. The same application works fine on other Solaris 10 machines.
Different environments mean just that. So something could be causing it outside java.
Additionally if anything at all is different in the execution data, such as even a name having a different size, then it would change the execution path.
Which would cause a problem in the JNI code to manifest itself on only one box. Probably isn't a pointer bug but all sorts of odd behavior can result from that.

Should I be able to see a priority change using a mutex priority ceiling

If I have a program which uses a mutex lock in solaris 9 which is set up to protect/priority ceiling of 5 and kick it off using priocntl with a priority of 11 and RT, I can look at top and see that it has priority 111. So my process is running real time. I then use a second xterm and wait till the program hits the lock portion of the code. If I do a priocntl -d pid, it is still priority 11. I know it is in the lock because there is a printf and a sleep of 20 seconds. Should I be able to see the priority go to 5? How can I prove the priority inheritance off the mutex lock is working in a test program? Thanks for any insight.

I also tried it with a priority ceiling of 50, figured out that RT priorities worked the reverse of regular priority, the higher the priority number, the higher the priority. I still however am not able to prove the priority inheritance occured. Anybody got any thoughts on how to prove it is working properly.

How to implement a "mutex" lock

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Hi,
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me=$$
while [ $me -ne 0 ]
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flagfile=batch1.flg
while [ $flagfile = $flagfile ]
do
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Mutex locking issue on Solaris 10

We are having a problem with mutex locking.
On one scenario we are running our application
On a v245 running Solaris 10 6/06 update 2 patch 118833-24
On our 5120 we are running Solaris 10 8/07 update 4patch 137111-05.
Our application creates several thousand simultaneous mutex inits (pthread_mutex_init). Approx 12 are locked at any one time. Our problem is after several min the application fails because the mutex destroy does not appear to destroy the mutex. This is true only on our 5120 but not on our v245. As a result our application runs fine on the v245 but fails quickly on the 5120.
Do you have any knowledge of why this might be happening?
Any help you can provide in this will be greatly appreciated.
If this is not the right group to post this messages please let me know.
Thanks!

How many threads do you have performing these mutex operations? The 5120 probably runs a lot more concurrent threads than the v245 does, so it's likely you're running into a race condition that's only apparent when the number of concurrent threads is large enough.
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You can use the race-condition tools that are part of Sun Studio 12 or another memory-checking application such as Purify to find out where your error may be. Given the timing issues apparently involved, those are probably your best options. The overhead of tools such as watchmalloc or even the run-time memory checker in Sun Studio may be too much and mask your timing issues. Assuming that's what the root cause of your problem is.
I didn't look at what's involved in destroying a process-shared mutex, though. That's a lot more complicated.
On edit: How do you know that pthread_mutex_destroy() is not destroying the mutex?
Edited by: AndrewHenle on Jun 16, 2009 3:46 PM

Multi processor Solaris 2.6 and mutex locks

hi,
is anyone aware of any documented issues with Solaris 2.6 running
on dual-SPARC processors (multi-processor environment) where the
programs using "mutex locks" (multi-threaded applications), require
some special handling, in terms of compiling and linking, to some
special libraries.
as far as i remember, in some OS book, maybe Peterson's, it was said
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regards,
banibrata dutta

I am also facing similar problem. Application which written using Mulit-Threaded using Posix Mutexes. When i run on SINGLE processor manchine, i.e.
SunOS sund4 5.7 Generic_106541-11 sun4u sparc SUNW,Ultra-5_10
It works perfectly.
But when try to run on dual processor machine, i.e.
SunOS sund2 5.7 Generic_106541-11 sun4u sparc SUNW,Ultra-250
It is blocking in the one of mutexes.
Please inform us what is problem. Mr. B. Datta, you comes to know
any channel, please inform me also at [email protected]
Thanx & regards,
-venkat

Critical Section Minus Synchronization

Without using synchronization would it be possible
to change these two classes so that each thread
takes it in turn to be in their criticall
sections i.e. one cannot take consecutive turns?
Thanks.
public class SharedVariables extends Object {
public int turn;
public boolean[] flag = new boolean[2];
public SharedVariables() {
flag[0] = false;
flag[1] = false;
// A thread running SectionedCode alternates between
// a critical section and the remainder.
public class SectionedCode implements Runnable {
int this_thread, other_thread;
SharedVariables s;
public SectionedCode( int tid, SharedVariables SV ) {
this_thread = tid;
other_thread = 1 - tid;
s = SV;
public void run() {
while ( true ) {
s.flag[this_thread] = true;
s.turn = other_thread;
while ( (s.flag[other_thread] == true) && (s.turn == other_thread) )
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System.out.println("Thread " + this_thread + " in remainder");
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I am not sure if i understand the question BUT if i have understood you correctly, you should be reading up on the join feature in threads

How To Use Recursion In Forms?

I have the following table
Table name: Project_Details:
Coulmns:
Project_num Number(6) PK
Project_Title
Project_status
Parent_project_Number Number(6) FK (It’s a foreign key for the project
number in the same table)
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Project Number: 100
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100
If any body has any idea in how to implement this idea using oracle forms and SQL please help me. Its urgent..
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Hmmm, looks like you can't update a connect by prior view. That's a shame.
Anyway, here's what you need:
CREATE TABLE test
(child number
,parent number);
INSERT INTO test VALUES (1, null);
INSERT INTO test VALUES (2, 1);
INSERT INTO test VALUES (3, 1);
INSERT INTO test VALUES (4, 2);
INSERT INTO test VALUES (5, null);
INSERT INTO test VALUES (6, 5);
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CREATE OR REPLACE VIEW test_hier_vw
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select lpad(' ',2*(level-1)) || to_char(child) hier
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2 /
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1
2
4
3
5
6
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8
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Please Help - Permutations using recursion..

Please some body help me in generating permutaions using recursion..exact guidelines are as follows..
Producing consecutive permutations.Need to develop a method that lists one by one all permutations of the numbers 1, 2, �, n (n is a positive integer).
(a) Recursive method . Given a verbal description of the algorithm listing all permutations one by one, you are supposed to develop a recursive method with the following header:
public static boolean nextPermutation(int[] array)The method receives an integer array parameter which is a permutation of integers 1, 2, �, n. If there is �next� permutation to the permutation represented by the array, then the method returns true and the array is changed so that it represents the �next� permutation. If there is no �next� permutation, the method returns false and does not change the array.
Here is a verbal description of the recursive algorithm you need to implement:
1. The first permutation is the permutation represented by the sequence (1, 2, �, n).
2. The last permutation is the permutation represented by the sequence (n, �, 2, 1).
3. If n a ,...,a 1 is an arbitrary permutation, then the �next� permutation is produced by
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(i) If the maximal element of the array (which is n) is not in the first position of the array, say i n = a , where i > 1, then just swap i a and i-1 a . This will give you the �next� permutation in this case.
(ii) If the maximal element of the array is in the first position, so 1 n = a , then to find
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Please help...i have trying this for long time
plesae help...i apreciate your time..and help..thank you

public class Permu {
    public static boolean nextPermutation(int a[]) {
            return(permute(a, 0));
    public static boolean permute(int v[], int start) {
         int n = v.length;
         if (start == (n - 1)) {       //if its the end of the sequence genereated then print them
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v[i] = temp;
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//of the n the first is kept constant the same is applied for the rest sequence
//int tmp = v[i];
v[i] = v[start];
v[start] = temp;
return true;
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int v[] = {1, 2};//this is the array which should contain the items      to be permuted
do{
for(int i=0;i<2;i++)
System.out.print(v[i]);
System.out.println();
}while(nextPermutation(v));
[i]Output:
123
123
123
123
123
This is exact code i am trying to run...pls someone help me out...

[ETA: posted in wrong forum, sorry! will repost in relevant forum] reading samples: critical section atomicity?

Hello all,
I have the following situation:
- one thread (T1) is constantly reading samples from a NI USB 9229 in a local buffer and copying them an array A (44100Hz)
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- array A is protected in a critical section (T1 and T2 enter the critical section when working with A directly and leave it afterwards)
How "atomic" is the reading of samples from the device in my array A? I.e., is it guaranteed that the critical section protection on A means that by the time T2 accesses A, T1 has finished writing 44100 samples in it?
Or do I have to register with DAQmxRegisterEveryNSamplesEvent() a callback which 1) reads 44100 samples, 2) notifies T2 that the batch is complete and available?
Thank you in advance!
Message Edited by acgrama on 02-08-2010 08:30 AM
Solved!
Go to Solution.

As far as I can understand the situation, the answer should be 'yes': the array is protected until you leave the critical section.
But could I suggest an alternative, perhaps simpler approach?
If you configure a thread safe queue of 44100 elements which discards old elements, with T1 that fills it on top, T2 can freely read from the queue without disturbing T1, having available the most recent set of data in any moment.
Proud to use LW/CVI from 3.1 on.
My contributions to the Developer Zone Community
If I have helped you, why not giving me a kudos?

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Implementing "critical sections" using recursive mutex locks

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