Robust Reader Writer Locks?

Does anyone know of an implmentation of robust reader/writer locks? (i.e. locks that unblock and return an error when the process that holds the lock dies) I found that Solaris supports robust mutex locks, but cannot find anything about robust reader/writer locks.
Thanks for the help!
Jason

It doesn't sound like you have a good background in concurrency yet. Take a look at this book.
http://java.sun.com/docs/books/cp/
Great book, great guy. Let me know if you need any help after you start.

Similar Messages

How to implement Reentrant Read Write Locking??

It seems like there should be a ReentrantReadWriteLock in Coherence. Am I missing some basic concept or something?
Thanks!

Hi,
there is no such thing as a shared lock on cache keys in Coherence out-of-the-box, at the moment, but it can be implemented on top of other features (with some performance decrease), but it is a fairly complex task, particularly the continuation of the client thread once the lock is acquired is tricky. Also that approach wouldn't be integrated with Coherence TransactionMap and JCA Adapter features, so in case you need such things you would need to reimplement those on top-of the custom read/write locking solution on your own.
Best regards,
Robert

Q. Reader-Writer lock across unrelated processes?

What mechanism would you suggest to implement Reader-Writer locks across unrelated processes?
Though the documentation for pthread_rwlock_ functions state
Synchronization Across Process Boundaries
Each of the synchronization primitives can be set up to be used across process
boundaries. This is done quite simply by ensuring that the synchronization variable is
located in a shared memory segment and by calling the appropriate init() routine,
after the primitive has been initialized with its shared attribute set as interprocess.
but they work only if the processes are forked off from a given process which initialized the relevant synchronization variable and not if the processes are totally unrelated.

What mechanism would you suggest to implement Reader-Writer locks across unrelated processes?
Though the documentation for pthread_rwlock_ functions state
Synchronization Across Process Boundaries
Each of the synchronization primitives can be set up to be used across process
boundaries. This is done quite simply by ensuring that the synchronization variable is
located in a shared memory segment and by calling the appropriate init() routine,
after the primitive has been initialized with its shared attribute set as interprocess.
but they work only if the processes are forked off from a given process which initialized the relevant synchronization variable and not if the processes are totally unrelated.

Could not obtain a maintenance-read + write-Lock for DBQueue/QStream/jobID

Hi All,
Does anyone know what does this error mean?
com.sap.b1i.xcellerator.XcelleratorException:
XCE001 Nested exception: com.sap.b1i.xcellerator.RejectedException:
XCE061 Could not obtain a maintenance-read + write-Lock for DBQueue/QStream/jobID Q.INB_IQ_INTQ_ASYN_QS.0010000000
Regards
Szymon

You see that's the thing, I'm not using it for a picture camera. The camera prob wouldnt read the card anyway. I'm using it as a storage device for my Nintendo Wii, I have files that I put on there to use as channels for my Wii Home Screen.

FileStream locks read & write access. How can I get around this?

I'm progressively downloading a video from a server using URLStream and FileStream classes to download and save the data to disk. While this is happening, I would also like to begin playback of the video so the user can progressively watch while this is happening. The player uses a standard FLVPlayback (version 2.5) control to load and playback videos. Unfortuantely, FileStream creates a read & write lock on the file and nobody has thus no one else can have access to it. This is a little bezarre to me because a read lock on a download is counter-intuitive, especailly for my application. I looked around the API docs but I could not find an option where I can manually set the locking mechanism on a file. Is this at all possible in Adobe AIR?

nef9877 wrote:
If I deathorise aall comuters and then re-authorise only the ones I want to use would this do it?
Yes, that's how it's done.
Read the warning about the number of times you can do this each twelve months. It can only be done so many times per year (I forget the exact wording).

How do I resolve this error message? The iPhoto library is on a locked volume. Reopen iPhoto when you have read/write access, or reopen iPhoto with the Option key held down to choose another library.

How do I resolve this error message? The iPhoto library is on a locked volume. Reopen iPhoto when you have read/write access, or reopen iPhoto with the Option key held down to choose another library.

Hi j,
I don't know if this will work, but I'd try logging in to an admin account, going to your main library (not user library), opening it, opening Application Support, selecting iPhoto, hold down the command key and press i, click on the lock in the lower left, entering the password and making sure you have Read & Write privileges for System and Admin.

This message shows up when I try to access my auxiliary iPhone library: "The iPhoto library is on a locked volume. Reopen iPhoto when you have read/write access, or reopen iPhoto with the Option key held down to choose another library."

This message shows up when I try to access my auxiliary iPhone library: "The iPhoto library is on a locked volume. Reopen iPhoto when you have read/write access, or reopen iPhoto with the Option key held down to choose another library."
What did I do wrong? I have been downloading all my photos into this same library since Janurary with no problems.

What version of Mac OS X?
Click the black Apple icon on the top left of the screen and select About This Mac. The next screen will show the information.

Is it possible to change the read/write permissions on a time machine back-up of iTunes? I need to restore it, but old version is locked....

Is it possible to change the read/write permissions on a time machine back-up of iTunes? I'm needing to restore it as my phone deleted half our playlists during sync & am not seeing a way to unlock the permissions. I have the current version unlocked, but can't seem to get the backed-up version. When I click on restore I get a pop-up that says iTunes can't be deleted as it is part of the OS. I'm not even trying to delete, just restore the old version. Any suggestions?

Hmmm, ok I'll give it a shot. I've always had the iTunes sync w/ my phone set up to only load selected playlists to the phone b/c there's a lot more in iTunes than I have room or desire for on my phone. A few months back I started having trouble w/ trying to sync everything & subsequently adding more to the phone than it could hold. The quickest thing at the time was to unclick the sync music option in iTunes so I could still backup the phone to the computer & not have a problem.
When I asked about it during one-to-one session shortly after, they advised me to delete the music off my phone & then re-sync it to the computer, run a backup of the phone & redownload the music to the phone. When I tried this it ended up deleting all my playlists (but not my husband's) from iTunes. Irritating, but I've been rebuilding the playlists since. I had also unclicked sync music again & an Apple person told me the most likely best fix was to delete & reload iTunes completely.
A few days ago I realized I hadn't backed up the phone to the computer in over a month so after deleting & reinstalling iTunes, & w/o changing anything (sync music was STILL unchecked) I ran a backup & my phone went from having 4 GB free space to being 2 GB over capacity due to iTunes trying to download the entire music library to the phone. I made a one-to-one appt again & it was suggested AGAIN that I delete all the music off my phone & then resync it to the computer & redownload the music. We did this (though a few random songs that had previously been purchased somehow remained on the phone), I got home, connected the phone & instead of the music that shows as 'on my device' disappearing from iTunes it just sat there, so, as the guy had told me I MIGHT have to do, I threw all those songs showing in iTunes as being on my phone, in the trash so that it was completely clear.
At this point I checked sync music, made sure the options were 'selected playlists only', checked the ones from my own list that I wanted (I usually have one playlist of comedians from my husband's folder that I also have on the phone, but didn't check it at this point). It uploaded all my stuff just fine, but for whatever reason when it saw that I wasn't uploading that comedy playlist any longer, it not only didn't upload it but proceeded to delete my husband's entire folder of playlists from iTunes. -_- I got on the phone w/ an Apple support person right away but he wasn't able to tell me anything .. basically said we'll have to rebuild everything. I asked about the possibility of using time machine, he said he's not qualified to answer that, so that's when I started looking around online & found, among others, the link I referenced a couple replies ago.
I hope this all makes sense. It's been a long-term issue so I'm trying to go from memory as I figured to begin w/ that I had just made a mistake somewhere, so didn't try to document anything. Now w/ it having happened a 2nd time, I'm not sure if it was 'user error' or something else.......

ICalExternalSync locks up my system with disk read/writes - any fixes?

When I allow ICalExternalSync to run it completely hangs up my system by hogging a gig of real memory and nearly 3 gigs of virtual memory. It also floods the system with continuous disk read/writes - which stop immediately when I quit the process.
I've learned to shut ICalExternalSync down in "Activity Monitor" as soon as I've synced my calenders.
Anyone else have this problem and a fix?

I thought so too, but after doing that, the total download size for the updates was bigger than the space left. It was 2.8 gigs of downloads, and the root partition was 5.6 gigs full out of 7.56 gigs.
I've never experienced such a huge update before! It's been a few hours and i'm still fixing it. There's literally hundreds of thousands of files that are now giving me "file exists in filesystem" errors so i'm making a script to delete all of those.
To get an idea of how many files there was, i outputted the errors to a file, opened it up with less, then pressed and held page down for almost 2 minutes, didn't reach the bottom, so ended up just pressing end.
Anyways, I'm going to post the scripts so it in case anyone encounters this critical problem, they can follow some simple instructions and be on their way.

How do is get back to Read & Write permissions on HDs ?

Hi gang,
I was trying to set up one central folder for 4 iTune users (accounts) in our household.
One of the blogs said put in "Shared" folder and set permissions to "Read & Write". I tried but on "Everybody" is does not offer the "R&W" option, just "Read". They also said to be sure you clicked "Apply to Enclosed Items" in the drop down. Although I could not set "Everyone" to "R&W", I clicked on "Apply to Enclosed Items" and the hard drives clicked for at least 15 minutes.
Afterward I got a pop up that said...   System Extension "/System/Library/Extension/ACard6280ATA.kext" was installed improperly and can be used. Try reinstalling. and an OK button to click. I clicked OK and at least 100 more popup appeared, one after the other as I clicked OK.   They all had the same basic message except the info after /System/Library/Extension/, it kept changing slightly on each new popup.
The big problem is I now have three of my four internal hard drives locked to my access and all they say custom on the permissions Privilege window.   Only my main HD is working, thank God.
How do I get back to Read & Write on Privileges, and on all Hard Drives?
Thanks for any help, I just made the move to MAC but have good background with windows operating system.
Gary

Thanks for all the reply's, I really appreciate your time. I have Apple Care so I worked with Apple tech last night and today, but they had to pass problem on to their engineers. They did a great job trying to help and spent 2 hours helping me input in code through the Terminal screen. It helped a little, but we still can access drive 2, 3 and 4 due to the global permissions that were changed.   All in all, it looks like we have to reinstall the OS on a washed HD.
I found out that the Repair program (Disk Utilities) only repairs permissions that were created after the initial set up. It won't correct original setting and that's what happened when I clicked on "Apply to Enclosed Items" at the root level. Likewise Time machine does not clone the main operating system so a restore would probably not get all the pieces back in their proper places.
I was thinking of doing a reinstall of the whole Mac HD drive (boot drive) with an exact copy I made with Carbon Cloner a month back, but the techs seem to think they will have to work on of the 4 individual HD I have.
Thanks again for the quick responses, I will let you know what happens in a few days.
Gary

How can I change read/write permissions for a DVD RW?

I've some files saved onto a DVD RW previously and would like to add on more files to it. However, it doesn't allow me to do that. When I checked the file info, it says that I have read & write privilege, but at the same time, there's another line that says "You can only read". When I clicked on the lock to attempt to make changes to settings, nothing is clickable. Take a look at the screenshot below and you'll know what I mean.
Can anyone advise on why this is happening?

A DVD-RW has to be wiped before re-use, so you will lose all data previously copied to it.

Installing Mountain Lion from Snow Leopard, Install failed and HD write-locked

I recently downloaded the mountain lion installer from the App Store and I ran the installer. Stupid person as I am, I did not have any backups for my file and I naively assumed that an apple OS installer would be without flaws. Boy, was I wrong. I need every bytes of my data (or close to every bytes) but the installer failed.
Mid installation, the installer stopped and said that the installation failed and that I need to repair my disk. So I restarted the computer and I ran disk utilities (my start up disk was the OS installer and the installer allows me to run several programs, including terminal, disk utilities, and by the way, when I held option while starting up to see which start up disks I have, I only had the OS installer as the start up disk. Also, the installer allows me to run a program called "Startup Disk" when I click on the apple logo on the top left corner, but it doesn't allow me to startup my computer using Macintosh HD) and noticed that when I highlighted Macintosh HD, my "Repair Disk" button was grayed out. So first things first, I ran the "Verify Disk" button but after a minute or so, Disk Utilities said that verification failed and that Macintosh HD needs to be repaired. But the "repair disk" button is grayed out! So I went to the Mountain Lion installer again and ran it. Of course, it failed again so I restarted the computer.
So I tried to first back up all files in Macintosh HD to an external hard drive using Disk Utilities, and I used features such as "New Image" and "Restore" but they both ended up in "Input/Output error". I tried many methods with Disk Utilities but they resulted in errors.
After some research, I noticed that some people's computers worked after they reset their PRAM. So that's what I did. I held command+option+P+R when computer started up and I reset the PRAM. When the start up disk (which is the OS installer, not the normal operating system) loaded, I was greeted with choose languages option and then I was back in the Mountain Lion installer state. I again ran the installer again, hoping something would be different, but then it was different. But not in a good way. When I was told to choose where I would like to install Mountain Lion, I noticed that Macintosh HD was grayed out. Last time, I was at least able to run the installer but this time, Macintosh HD was grayed out. The installer said that my Macintosh HD was locked. After some research, I learned that apparently, the Mountain Lion installer write-locks Macintosh HD mid installation.
So now I am stuck and I am thinking of two things (plus some questions)
1. I am wondering if there is a way to unlock Macintosh HD. But even if I can unlock Macintosh HD, there is no guarantee that the installer will successfully install Mountain Lion, am I right?
a. so how can I un-write-lock Macintosh HD?
2. More realistically, I am thinking of borrowing someone else's macintosh computer and use it as the backup center. I have a firewire cable and a terrabyte external hard drive. So what I'm thinking is that I'll hook my computer in target mode to my friend's computer and I will also plug in my external hard drive to my friend's computer and then I can download and run Carbon Copy Cloner from my friend's computer to copy all data from my Macintosh HD to my external hard drive. And then I will erase my Macintosh HD, freshly install Mountain Lion onto it and then copy all data back from my external hard drive. But I am not sure about few things.
a. it looks like my Macintosh HD is write-locked. Can I still use Carbon Copy Cloner to copy all data from Macintosh HD (in target mode) to my external hard drive?
b. will my computer allow me to erase (or format) Macintosh HD?
c. will my erased/formatted Macintosh HD able to install + be installed Mountain Lion OS?
If you are here, then you have read my long long problem. Thank you very much and I would really really really appreciate your answers and opinions. Thanks

I'm not sure where you read that about the disk being "write-locked." That doesn't make much sense, given that the major task an installer like this must achieve is writing a whole bunch of files to the hard drive. I think your source was mistaken.
As to what happened, it sounds like your hard drive was badly corrupt to start with, or possibly was on the edge of failing and is now in the process of dying entirely. If you don't have backups of your data, that does not bode well for you, unfortunately. If you can manage to use target mode to copy your data, do that.
Once you're sure you've got all your data, you need to start up from your Snow Leopard install disk and repair the hard drive. (Since it sounds like the Mountain Lion installer didn't work, I wouldn't trust the recovery partition that Mountain Lion installs.) Or, even better, just erase the hard drive entirely and reinstall Snow Leopard. Then, once you're back up and running, with all your data back on the system and with Snow Leopard updated to the most recent version, try installing Mountain Lion again. If any of that fails again, the problem is likely to be a dying hard drive, and you'll need to replace it.

How do I allow users to create folders in a shared folder where we all then have read/write access to those new folders?

I have three users who need to access a particular folder on one of our other Macs. The folder resides on the desktop of that particular Mac and it is set as "shared" with all of our accounts set to access the folder. When a user creates a new subfolder in that shared folder, the permissions are instantly set to allow the creator read/write access but the other users are only allowed read-only access. Is there a way to set the permissions so that any new folder created in that shared folder automatically gives read/write access to all accounts who are authorized access to that shared folder?

You should be able to take the permissions you have set and "apply to enclosed items." I am trying to attach a picture of what this looks like so my apologies if it does not work.
Highlight your folder you want and go to File>Get Info or command+I and at the bottom where it has Sharing and Permissions, click the lock button to authenticate. Click the gear and click "apply to enclosed items". See if that works.

Can't update photos using iPhoto 6 - read/write permissions

Help!
Before you think this is the standard "iPhoto 6 permissions problem", please read on.
Upon installing iPhoto 6 and attempting to update my iPhoto Library, I get the dreaded "There is a problem accessing...files in your iPhoto Library folder...Make sure you have read and write permissions for the folder...all enclosed items." This is the problem noted in:
http://docs.info.apple.com/article.html?artnum=303135
However, it doesn't tell me what file(s) have the problem, even though the app note says it would for OS 10.3.9. No matter. I simply first did a get info on the iPhoto Library folder verified that it was not locked and that I had read/write permissions. I also applied that to everything inside the folder. Ran iPhoto again...same error.
Although I didn't get the "repair permissions" error, I did that too. Ditto for the locked files issue reported at:
http://docs.info.apple.com/article.html?artnum=303232
After attempting the update at least a dozen times, I even tried the UNIX chmod command (774) on everything in the iPhoto Library folder just in case the "get info" method didn't take. Still get the same error when updating iPhoto 6. What gives!
I willing to try any suggestions ya'll might have!
FYI - I do have my older version of iPhoto available and I have a complete backup of my iPhoto Library.
Thanks!
david

Hi David,
It's up to you, unless someone else comes along with some more things to try.
I am assuming you still have a version 5 of the iPhoto Library folder in the Finder.
Rename it to iPhoto Library_old and drag it to the desktop.
Do a search in the library for Thumbs. this will find all the Thumb folders which you do not want to import into the new Library. Delete those Thumb folders.
Now you have to decide if you want to import both the Original and Modified versions of a photo, or just the Originals. The problem is, if you import both, they will no longer be linked but will show up as separate photos in the library.
Actually it is going to be a big pain unless you have just the photos backed up to reimport.
If you want, you can check out a page I made showing the manual way to import the photos (#3)
http://homepage.mac.com/loridilo/iPhoto5help/Personal22.html

DVD-RAM read/write in OSX 10.8.2

I have a number of disks in the DVD-RAM format which are backups from a family member. I need to resurrect this now dated, but still quite effective DVD standard. I have acquired a later Model Matshista (Panasonic) drive, Model SW-9576S, one of their faster and more recent DVD-RAM cartridge drives. It is housed in a new IDE=>USB enclosure. It works fine on my 17" MBP using Win 7 in bootcamp, both reading and writing. I believe I have an OSX software problem, since on the Mac side of the machine, the drive mounts, and files can be seen, but they cannot be read, and I cannot write a file to new media. All of these cartridge DVD-RAM disks come from the factory formatted as "UDF". I tried to format one for the Mac using disk utility, but it did not work, returning a disk error message and not allowing the format.
I know this is supposed to work, and DVD-RAM standard is still supported. It has some advantages, particularly its ability to function as a hard drive with unlimited read/write cycles.
I would be grateful for any help....

DVD-RAM cartridges have a lock button for physical access to read/write. Look for it.
MOST 3rd party DVD recorders from Samsung and others will read/write DVD-RAM in modern units. Check their specs. The Apple Superdrive does NOT work with DVD-RAM
There is more issues about compatibility from the external USB 2.0 drive case onboard chip talking with USB 3.0 machine than with the Panasonic unit.
You can remove the DVD from the case and try using it in the unit as well. The case just functions as an extra protection for fingers and dust.
IF it mounts, work with Disk Utility to check its abilities. If you can see it, and choose to Repair Disk successfully, its working. If it gives you trouble to READ it, try a better enclosure/connection type like those from OWC or Mac knowledgeable sellers.
Regards,

Robust Reader Writer Locks?

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