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  • Is pthread_spin_trylock safe inside of sigsegv handler of multithreaded application?

    - by TWMouton
    I am trying to implement a handler that on SIGSEGV will collect some information such as process-id, thread-id and a backtrace and write this information to a file/pipe/socket. The problem lies in that there is the (probably pretty high) possibility that if one thread experienced a SIGSEGV that the others will shortly follow. If two threads happen to make it to the bit of code where they're writing their report out at the same time then they'll interleave their writing (to the same file). I know that I should only be using async-signal-safe functions as detailed in signal(7) I also have seen at least two cases here and video linked in top answer here where others have used pthread_spin_trylock to get around this problem. Is this a safe way to prevent the above problem?

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  • Pthread - setting scheduler parameters

    - by Andna
    I wanted to use read-writer locks from pthread library in a way, that writers have priority over readers. I read in my man pages that If the Thread Execution Scheduling option is supported, and the threads involved in the lock are executing with the scheduling policies SCHED_FIFO or SCHED_RR, the calling thread shall not acquire the lock if a writer holds the lock or if writers of higher or equal priority are blocked on the lock; otherwise, the calling thread shall acquire the lock. so I wrote small function that sets up thread scheduling options. void thread_set_up(int _thread) { struct sched_param *_param=malloc(sizeof (struct sched_param)); int *c=malloc(sizeof(int)); *c=sched_get_priority_min(SCHED_FIFO)+1; _param->__sched_priority=*c; long *a=malloc(sizeof(long)); *a=syscall(SYS_gettid); int *b=malloc(sizeof(int)); *b=SCHED_FIFO; if (pthread_setschedparam(*a,*b,_param) == -1) { //depending on which thread calls this functions, few thing can happen if (_thread == MAIN_THREAD) client_cleanup(); else if (_thread==ACCEPT_THREAD) { pthread_kill(params.main_thread_id,SIGINT); pthread_exit(NULL); } } } sorry for those a,b,c but I tried to malloc everything, still I get SIGSEGV on the call to pthread_setschedparam, I am wondering why?

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  • What are the different file permission codes and what do they mean?

    - by zeckdude
    I am working with a file upload script. I am currently uploading a file and then trying to echo out an anchor linking to that file, but since I used mkdir() with 0700 permissions to upload the file, it won't allow me access to view the file. I am pretty sure the problem I am experiencing is because of the file permission code I used. The problem is I just don't know what all the different file permission codes are and what they mean. Can somebody please list out all the different file permissions and what they each do?

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  • How to list library dependencies of a non-native binary?

    - by lvella
    When developing for native platform, I can use ldd to list all the shared libraries (.so files) a binary executable I build will try to load upon start-up. But when cross-compiling, I don't know how to get the same information. The ldd is not a normal binutils utility, like strip or ar, that can be built alongside gcc for cross compiling, but instead, it is a cryptic shell script that apparently can only run on native platform. So, using the cross-target binutils tools, is there any way to get a list of the dynamically linked dependency for of a foreign binary?

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  • Why does my Perl TCP server script hang with many TCP connections?

    - by viraptor
    I've got a strange issue with a server accepting TCP connections. Even though there are normally some processes waiting, at some volume of connections it hangs. Long version: The server is written in Perl and binds a $srv socket with the reuse flag and listen == 5. Afterwards, it forks into 10 processes with a loop of $clt=$srv->accept(); do_processing($clt); $clt->shutdown(2); The client written in C is also very simple - it sends some lines, then receives all lines available and does a shutdown(sockfd, 2); There's nothing async going on and at the end both send and receive queues are empty (as reported by netstat). Connections last only ~20ms. All clients behave the same way, are the same implementation, etc. Now let's say I'm accepting X connections from client 1 and another X from client 2. Processes still report that they're idle all the time. If I add another X connections from client 3, suddenly the server processes start hanging just after accepting. The first blocking thing they do after accept(); is while (<$clt>) ... - but they don't get any data (on the first try already). Suddenly all 10 processes are in this state and do not stop waiting. On strace, the server processes seem to hang on read(), which makes sense. There are loads of connections in TIME_WAIT state belonging to that server (~100 when the problem starts to manifest), but this might be a red herring. What could be happening here?

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  • Operations on 64bit words in 32bit system

    - by Vilo
    I'm new here same as I'm new with assembly. I hope that you can help me to start. I'm using 32bit (i686) Ubuntu to make programs in assembly, using gcc compiler. I know that general-purpose-registers are 32bit (4 bytes) max, but what when I have to operate on 64 bit numbers? Intel's instruction says that higher bits are stored in %edx and lower in %eax Great... So how can I do something with this 2-registers number? I have to convert 64bit dec to bin, then save it to memory and show on the screen. How to make the 64bit quadword at start of the program in .data section?

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  • TERM environment variable not set

    - by rahkarp
    I'm using python to develop an app and want to view running processes.The code txt = commands.getoutput("top -d 1") print txt gives an error "TERM Environment Variable not set" Can someone tell me what this means and how to solve this

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  • ffmpeg: create a video from images

    - by vailen
    Is it possible to use ffmpeg create a video from a set of sequences, where the number does not start from zero? For example, I have some images [test_100.jpg, test_101.jpg, test_102.jpg, ..., test_200.jpg], and I want to convert them to a video. I tried the following command, but it didn't work (it seems the number should start from zero): ffmpeg -i test_%d.jpg -vcodec mpeg4 test.avi Any advise?

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  • Python script not working when run from browser directly

    - by splatterdash
    I'm trying to run this script: import re, os def build_pool(cwd): global xtn_pool, file_pool xtn, xtn_pool = re.compile('\\.[0-9a-zA-Z]{1,4}$'), [] file_pool = [files for files in os.listdir(cwd) if os.path.isfile(files) and xtn.search(files)] # Lists all the file extension in the folder for file in file_pool: if not xtn_pool.__contains__(xtn.search(file).group()): xtn_pool.append(xtn.search(file).group()) return xtn_pool.sort(), file_pool if __name__ == '__main__': import sys #if path is given, change working directory to path if len(sys.argv) >= 2: os.chdir(sys.argv[1]) build_pool(os.getcwd()) #if no path is given when running, do renaming in current folder else: build_pool(os.getcwd()) print('The folder contains the following extensions: ') for i in range(0, len(xtn_pool)): print(repr(i+1) + '. ' + xtn_pool[i][1:]) opt = int(input('Which one would you like to replace? ')) xtn_pick = xtn_pool[opt-1] # Lists all the file with the chosen extension xtn_file_pool = [file for file in file_pool if file.endswith(xtn_pick)] print('There are {0} files with the {1} extension.'.format(len(xtn_file_pool), xtn_pick)) xtn_new = input('Input replacement extension: ') # The actual renaming process for file in xtn_file_pool: os.rename(file, file[:-len(xtn_pick)+1] + xtn_new) directly from my file browser (Nautilus), but for some reason it's not working. When I run it from terminal (python3 scriptname.py) it works fine as intended. But when I just click the script file in Nautilus, choose 'Run in Terminal', it always stops after asking 'Input replacement extension: '. How can I make this script run without using the terminal?

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  • Create Directory, 'cd' to it and download a file pipeline in Perl

    - by neversaint
    I have a file that looks like this: ftp://url1/files1.tar.gz dir1 ftp://url2/files2.txt dir2 .... many more... What I want to do are these steps: Create directory based on column 2 Unix 'cd' to that directory Download file with 'wget' based on column1 But how come this approach of mine doesn't work while(<>) { chomp; my ($url,$dir) = split(/\t/,$_); system("mkdir $dir"); system("cd $dir"); # Fail here system("wget $url"); # here too } What's the right way to do it?

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  • Which not displaying location of executible actually run.

    - by Nick
    I have a version of SVN on my system in /usr/bin/svn. This is too old to use with some repositories so I compiled a newer version in /home/user/built/bin/svn which works fine. I added this to my PATH so it should be run first. Typing which svn produces /home/user/built/bin/svn however typing svn --version reveals that it us using the old version still. if I run /home/user/built/bin/svn --version then the correct version is displayed. Since the custom version is first in my $PATH, and which lists it first why is the older version being invoked when I run svn? I thought which used your $PATH to find executables in the same fashion as the shell? [Edit] Type gives: type svn svn is hashed (/usr/bin/svn) Is this the problem?

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  • Possible to view PHP code of a website?

    - by Camran
    Is it possible to somehow view another websites php files/codes? Or to rephrase the question, Can my php codes be viewed by anybody except for those who have access to the file? If so, how cant I best prevent this? Thanks Ps: Server OS is Ubuntu 9.10 and PHP version is 5+ (Apache2)

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  • What is the Effect of Declaring 'extern "C"' in the Header to a C++ Shared Library?

    - by Adam
    Based on this question I understand the purpose of the construct in linking C libraries with C++ code. Now suppose the following: I have a '.so' shared library compiled with a C++ compiler. The header has a 'typedef stuct' and a number of function declarations. If the header includes the extern "C" declaration... #ifdef __cplusplus extern "C" { #endif // typedef struct ...; // function decls #ifdef __cplusplus } #endif ... what is the effect? Specifically I'm wondering if there are any detrimental side effects of that declaration since the shared library is compiled as C++, not C. Is there any reason to have the extern "C" declaration in this case?

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  • How to programmatically switch to a specific window in compiz?

    - by FossilBit
    Is there a command to tell compiz that we want to bring in front and set focus to a specific window? How should we identify the window in that command? The reason behind this question is the following use-case: Suppose we have a wiki to keep notes of anything interesting we find out. It would be very convenient to have a keyboard shortcut to bring the browser window with our Wiki page in front and start typing immediately then with another key combination switch to the application we were working before I know that "ALT+TAB" switches between the last two used windows but cannot support more complex combinations of applications. E.g Browser+Eclipse+ Wiki If there is a command like the one described, it is easy to add a shortcut to it from KDE or GNOME interface Thanx ...

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  • Implemenation of a pass through file system

    - by user3491505
    Can anyone give me inputs on how to implement a pass through filesystem using fuse?? What I mean by this is that you mount your FUSE file system somewhere (say in /mnt) such that the FUSE file system passes all filesystem calls to some other place (say /home/user). For example, when you go into the /mnt directory and run "ls", this would pass the file system calls to execute ls through and run them on /home/user, such that the directory contents of /home/userwould be listed

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  • Why doesn't a 32bit .deb package install on 64bit Ubuntu?

    - by codebox_rob
    My .deb package, built on 32-bit Ubuntu and containing executables compiled with gcc, won't install on the 64-bit version of the OS (the error message says 'Wrong architecture i386'). This is confusing to me because I thought that in general 32-bit software worked on 64-bit hardware, but not vice-versa. Will it be possible for me to produce a .deb file that I can install on a 64-bit OS, using my 32-bit machine? Is it just a matter of using the appropriate compiler flags to produce the executables (and if so what are they), or is the .deb file itself somehow specific to one processor architecture?

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  • Bash command that prints a message on stderr

    - by Salman A
    I want to know if there is a built-in BASH command that prints some text on stderr, just like the echo command that prints text on stdout. I don't want to use temporary io-redirection. I use a built-in command to generate an error on stderr such as ls --asdf (ls: unrecognized option '--asdf') but I want something neater,

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  • perf events documentation

    - by Thanatos
    I've searched for an exhaustive explanation of the meaning of each event monitored by the perf stat command; I've found a tutorial which explains quite well how to use different the features of the perf tool. However, it doesn't explain the meaning of several events that can be observed (and there are a lot!!). Someone know where is a quite simple and complete documentation about the events listed by the perf list command? In particular, I'm interested in finding out the percentage of cpu used by some application I wrote. Can i measure it directly through cpu-clock or task-clock? What's the meaning of these two events? Thanks in advance

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  • Is this safe? Is this OK to do in MYSQL?

    - by alex
    I have always done this: mysqldump -hlocalhost -uuser -ppass MYDATABASE > /home/f/db_backup/MYDATABASE.sql mysql -uuser -ppass MYDATABASE < MYDATABASE.sql But, if I do this instead...is this safe? Is this identical to the above??? mysqldump -hlocalhost -uuser -ppass MYDATABASE | gzip > /home/f/db_backup/MYDATABASE.sql.gz zcat MYDATABASE.sql.gz | mysql -uuser -ppass MYDATABASE

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  • Curl: How to insert value to a cookie?

    - by Crazy_Bash
    Ho to insert cookies value in curl? from firebug "request headers" i can see in the following "Cookie: PHPSESSID=gg792c2ktu6sch6n8q0udd94o0; was=1; uncheck2=1; uncheck3=1; uncheck4=1; uncheck5=0; hd=1; uncheck1=1" I have tried the following: curl http://site.com/ -s -L -b cookie.c -c cookie.c -d "was=1; uncheck2=1; uncheck3=1; uncheck4=1; uncheck5=0; hd=1; uncheck1=1" > comic and the only thing i see in cookie.c is PHPSESSID=gg792c2ktu6sch6n8q0udd94o0; was=1;

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