February 2009 - Darwin-dev - lists.apple.com

Waking up a network server: 2 threads + semaphore vs 1 thread + pipe
by Joel Reymont 14 Feb '09

14 Feb '09

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:from:to :content-type:content-transfer-encoding:mime-version:subject:date :x-mailer; bh=Cs9kzSqMUCaVlkBh+K81Fwb1sawaWFAujGbMLA9odEw=; b=x0qK1IS0/b16N1GYa16alxjqkjYKQ4nYEOwFcK8kO+Fn7efiWeqoXO2l10O+yk5nFa 5Lb2rFzEGYRNakbFzZvKQ8bitQJ0kNcY4Mn9/rDUCzGXhd9Vu75gXdGD+555pD5z2Slp J+xzvzqwXXtoiKBnk6io0u9PkHzXtU3DFVsQk= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:from:to:content-type:content-transfer-encoding :mime-version:subject:date:x-mailer; b=Uw09feROU0dZdUk8GGhWPdLPstIy9wpSIHvIdbbJXa6RXmMlLAujkoaGAeh6MmT49C L5UailDdM9UloVo4nN5LeKasDE/e8Oqu/SBMCoUne91wc0eQLfeoi0N/JtqDgARiuqqV DzBoKm0WS7SPAGPGxviSUvLsDf8pHdzD0jATs= Which is the best design and how efficient? Thanks in advance, Joel --- http://tinyco.de --- Mac & iPhone _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… Suppose I'm trying to create a very efficient network server. I define efficiency as low latency and low CPU usage. The server is to run on the iPhone. The server will use one ring buffer each for sending and receiving data. I don't think it matters whether it's TCP or UDP for the purpose of this discussion. A producer is pumping out packets at high speed and there a main GUI thread with a run loop. One design would involve adding a CFSocket per connection to the run loop and using a separate thread and a semaphore to notify the network server that there's data to be broadcast to clients. I'm not sure if each CFSocket creates a separate thread or there's a thread managing all of them together. Not sure if it matters. There are at least two threads in this design and separate threads for network sending and receiving. Another design could use a pipe to wake up the network server and add it to the list of native sockets monitored by the server. This design could use either select or kqueue/kevent and may not need CFSocket. Sending and receiving here would run in a single thread since the pipe is just another descriptor to be monitored. How efficient is it to put a byte into a pipe in a callback that gets triggered every few milliseconds? Would there be a significant gain since an extra thread is not required to wait on a semaphore? Would it even out since (intuitively) a pipe is slower? This email sent to site_archiver(a)lists.apple.com

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PAM and the loginwindow.app
by Patrice Matthias Brend'amour 13 Feb '09

13 Feb '09

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Does any of you know how to get this working? Or has anyone an other solution for my problem? Best regards Patrice Brend'amour --- Patrice Matthias Brend'amour patrice.brendamour(a)uni-konstanz.de Department of Computer & Information Science University of Konstanz, Germany --- _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… This email sent to site_archiver(a)lists.apple.com Hi. I'm currently integrating 10 iMacs in an existing Linux computer pool for our students at the University of Konstanz. There we have an LDAP Server for authentication, no AD, no NFS/AFP. Authentication on OS X with LDAP works fine but I have a little problem with the homedirectories. Our sysadmins want me to mount the users home dir via sshfs to the mac. So far, no problem. Sshfs works on OS X. But we need to mount the homedir at login time (with the password). On linux I can do this via a PAM module: pam-mount. I managed to get the module working on OS X (it was is little bit tricky, because the module wasn't ever tested on OS X. I had to change a little bit of the c++ code until it worked properly) Now I can automount/unmount the users homedir when I login/logout on the iMacs via ssh/terminal. The problem is: Loginwindow doesn't seems to use PAM. There has been an plugin for loginwindow to enable PAM in the past but was removed from opensource.apple.com smime.p7s PGP.sig

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Re: query on stack trace
by Shawn Erickson 13 Feb '09

13 Feb '09

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:cc:content-type :content-transfer-encoding; bh=jrBaQwFAzlSjt0Z6nElFjjn80Nufeox/6Zw26sfVQIM=; b=XPQg9wkeDAzPHFrczK9ROt7ssrqNs0+Aben+h/I/ZWNwL/ZXqmGlQmWNQ+HTHIqzwV I71/ZyWrQrXMSHIrBIjfo/9KLApUwTAlNT1G4qvDw2sHRxY4uhtz2RhA1y/ewWgAamnT rwtnURl2axvHQ8psqD6GBhiWnL1n1WRqh8uGs= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=JnbczIZnnKf3AudbLBW1cIJ521dKiAFcgwxZyjPphCNvLHpewafoTk+euRpa5QzrpM zC4p9pAlXFtI6MgX8sJm24bSf+WdpsHTjGY+1SXXu8ecc3QZKNwlw9hUhwA8geb8NIMs FgsS+Xp9woIF2+eQvjWsHFh6bJmU1JvoC5kvA= On Fri, Feb 13, 2009 at 5:43 AM, Arnab Ganguly <aganguly01(a)gmail.com> wrote: > Thanks for all details.What does these numbers "795,574" refers to in the > atos output. > 0x9450366b -[NSApplication run] (in AppKit) + 795 > > 0x944d08a4 NSApplicationMain (in AppKit) + 574 The + <some number> is the byte offset from the start of the symbol or address to the left of the +. -Shawn _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… This email sent to site_archiver(a)lists.apple.com

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Re: query on stack trace
by Arnab Ganguly 13 Feb '09

13 Feb '09

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Re: query on stack trace
by Terry Lambert 13 Feb '09

13 Feb '09

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com This technote explains things: <http://developer.apple.com/technotes/tn2004/tn2123.html> -- Terry 1) Generate Debug Symbols = YES 2) DEBUG_INFORMATION_FORMAT = dwarf-dsm 3)STRIP_STYLE = all If any additional thing I need to take care also? -A Distribute a release build without a stripped symbol table? You can't really get symbols without a table to look them up from. -- Terry -- Terry 0x9450366b -[NSApplication run] (in AppKit) + 795 0x944d08a4 NSApplicationMain (in AppKit) + 574 0x2f1d 0x00002f1d (in App) 0x2852 0x00002852 (in App) 0x2779 0x00002779 (in App) What would be the workaround for this? Thanks in advance. -A _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/tlambert%40apple.com This email sent to tlambert(a)apple.com _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… On Feb 12, 2009, at 11:29 PM, Arnab Ganguly wrote: In the Xcode build settings should I make the following setting under the release build On Fri, Feb 13, 2009 at 12:47 PM, Terry Lambert <tlambert(a)apple.com> wrote: On Feb 12, 2009, at 11:14 PM, Arnab Ganguly wrote: Problem is that my application is an embedded application.So once the main application crashes, from my embedded application I try to run an atos on the main application to get the symbol information.What would be the best and correct approach to get the symbols resolved correctly from the main app,considering it has to be a release build? I don't have the opportunity to use backtrace set of functions as it is on Tiger and using 10.4 sdk.I am trying to retrieve the program counter and on that I run atos with the main applications process id. Thanks in advance -A On Thu, Feb 12, 2009 at 11:14 PM, Terry Lambert <tlambert(a)apple.com> wrote: Use the -o option to specify the object file for the program from which you have not stripped symbol information. It's able to print symbols for the libraries because their LC sections refer to files from which symbol information has not been stripped, bug the address yo are looking at is in a Mach-o object for which there us not symbol information on the disk. It more or less states that this will happen for stripped objects in the atos man page. On Feb 12, 2009, at 4:03 AM, Arnab Ganguly <aganguly01(a)gmail.com> wrote: Hi All, I am using atos with process id and the address but it returns me only the same hex address I am not getting the function name and the line number.Below I have given the output. The command that I am using is atos -p processid address. This email sent to site_archiver(a)lists.apple.com

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Re: query on stack trace
by Arnab Ganguly 13 Feb '09

13 Feb '09

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Re: How Mutexes Work
by Terry Lambert 13 Feb '09

13 Feb '09

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Lastly and perhaps most important, is there a good low-level OS book that might explain the nitty gritty when it comes to locks and everything else deep under-the-hood? UNIX Internals: The New Frontiers Uresh Vahalia Prentice Hall ISBN: 0131019082 ...chapter 7 covers locks pretty in depth. -- Terry _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… On Feb 12, 2009, at 6:34 PM, Dave Keck wrote: I'm pretty partial to a book that has a broad overview of techniques used by various OSs: (Disclaimer: I did technical review for Prentice Hall on the thing prior to publication). This email sent to site_archiver(a)lists.apple.com

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Re: query on stack trace
by Terry Lambert 13 Feb '09

13 Feb '09

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Distribute a release build without a stripped symbol table? You can't really get symbols without a table to look them up from. -- Terry -- Terry 0x9450366b -[NSApplication run] (in AppKit) + 795 0x944d08a4 NSApplicationMain (in AppKit) + 574 0x2f1d 0x00002f1d (in App) 0x2852 0x00002852 (in App) 0x2779 0x00002779 (in App) What would be the workaround for this? _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… On Feb 12, 2009, at 11:14 PM, Arnab Ganguly wrote: Problem is that my application is an embedded application.So once the main application crashes, from my embedded application I try to run an atos on the main application to get the symbol information.What would be the best and correct approach to get the symbols resolved correctly from the main app,considering it has to be a release build? I don't have the opportunity to use backtrace set of functions as it is on Tiger and using 10.4 sdk.I am trying to retrieve the program counter and on that I run atos with the main applications process id. Thanks in advance -A On Thu, Feb 12, 2009 at 11:14 PM, Terry Lambert <tlambert(a)apple.com> wrote: Use the -o option to specify the object file for the program from which you have not stripped symbol information. It's able to print symbols for the libraries because their LC sections refer to files from which symbol information has not been stripped, bug the address yo are looking at is in a Mach-o object for which there us not symbol information on the disk. It more or less states that this will happen for stripped objects in the atos man page. On Feb 12, 2009, at 4:03 AM, Arnab Ganguly <aganguly01(a)gmail.com> wrote: Hi All, I am using atos with process id and the address but it returns me only the same hex address I am not getting the function name and the line number.Below I have given the output. The command that I am using is atos -p processid address. Thanks in advance. -A _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/tlambert %40apple.com This email sent to tlambert(a)apple.com This email sent to site_archiver(a)lists.apple.com

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Re: query on stack trace
by Arnab Ganguly 13 Feb '09

13 Feb '09

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Re: How Mutexes Work
by Greg Parker 13 Feb '09

13 Feb '09

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Today, for some reason or another, I've been pondering how locks work. After locating the pthread source (in libc, available at opensource.apple.com, for those curious) I've found the source for the pthread_mutex_lock, in pthread_mutex.c It seems the meat of this function are the macros 'LOCK' and 'PLOCKSTAT_MUTEX_ACQUIRE'. The 'LOCK' macro is defined (indirectly) as _spin_lock. _spin_lock is implemented in various places based on the architecture you're compiling for; in my case I'm interested in i386. For that, _spin_lock is defined as: _OSSpinLockLock: _spin_lock: __spin_lock: movl $(_COMM_PAGE_SPINLOCK_LOCK), %eax jmpl *%eax .align 2, 0x90 .globl _OSSpinLockUnlock .globl _spin_unlock .globl __spin_unlock But I can't seem to find what _COMM_PAGE_SPINLOCK_LOCK is. I'm taking a shot in the dark that it's a function address in the kernel's address space. Is this correct? (I'm no assembly expert! :)) If so, where is the value for _COMM_PAGE_SPINLOCK_LOCK set? Secondly we have PLOCKSTAT_MUTEX_ACQUIRE. I can't seem to find where it's defined either, and it seems to be the real heavy-lifter for pthread_mutex_lock. Any ideas? Lastly and perhaps most important, is there a good low-level OS book that might explain the nitty gritty when it comes to locks and everything else deep under-the-hood? -- Greg Parker gparker(a)apple.com Runtime Wrangler _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… On Feb 12, 2009, at 6:34 PM, Dave Keck wrote: The "comm page" is an area of memory in user space which is shared across all processes and whose contents are controlled by the kernel. It's used for various low-level bits of code like memcpy and spinlock that are tuned carefully for machine-specific details such as CPU type and processor count. Code for at least some of the comm page's functions is in xnu/osfmk/ <arch>/commpage/ . spinlock for i386 is xnu/osfmk/i386/commpage/ spinlocks.s, where there are versions optimized for single- and multi- processor machines, both 32- and 64-bit. Ignore anything plockstat-related. That's just a hook for lock statistics via dtrace, and I don't even know if it's enabled by default. pthread_mutex is based on spinlocks plus either Mach semaphores or kernel mutexes, depending on the pthread mutex attributes requested. Amit Singh's Mac OS X Internals (http://osxbook.com) contains more nitty gritty than you can shake a stick at, but I don't know what his pthreads discussion looks like. Any OS textbook should be a good source for the general ideas of how to write synchronization primitives like spinlock or compare-and-swap and then build higher- level constructs with them. This email sent to site_archiver(a)lists.apple.com

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