race-condition

This question is based on: When is it safe to destroy a pthread barrier? and the recent glibc bug report: http://sourceware.org/bugzilla/show_bug.cgi?id=12674 I'm not sure about the semaphores issue reported in glibc, but presumably it's supposed to be valid to destroy a barrier as soon as pthread_barrier_wait returns, as per the above linked question. (Normally, the thread that got PTHREAD_BARRIER_SERIAL_THREAD , or a "special" thread that already considered itself "responsible" for the barrier object, would be the one to destroy it.) The main use case I can think of is when a barrier is used

I'm coding my Google Chrome Extension where I set the app's icon from the background script as such: try { objIcon = { "19": "images/icon19.png", "38": "images/icon38.png" }; chrome.browserAction.setIcon({ path: objIcon, tabId: nTabID }); } catch(e) { } Note that I wrapped the call in try/catch block. Still, sometimes I'm getting the following message in the console log: Unchecked runtime.lastError while running browserAction.setIcon: No tab with id: 11618. It's hard to debug this error because it seems to come up only when I close or reload the Chrome tab, it doesn't have a line number or any

The documentation for the Valgrind thread error detection tool Helgrind, found here warns that, if you use GCC to compile your OpenMP code, GCC's OpenMP runtime library ( libgomp.so ) will cause a chaos of false positive reports of data races, because of its use of atomic machine instructions and Linux futex system calls instead of POSIX pthreads primitives. It tells you that you can solve this problem, however, by recompiling GCC with the --disable-linux-futex configuration option. So I tried this. I compiled and installed to a local directory ( ~/GCC_Valgrind/gcc_install ) a new GCC version

How should one handle a possible race condition in a model's save() method? For example, the following example implements a model with an ordered list of related items. When creating a new Item the current list size is used as its position. From what I can tell, this can go wrong if multiple Items are created concurrently. class OrderedList(models.Model): # .... @property def item_count(self): return self.item_set.count() class Item(models.Model): # ... name = models.CharField(max_length=100) parent = models.ForeignKey(OrderedList) position = models.IntegerField() class Meta: unique_together =

I'm trying to implement (what I think is) a pretty simple data model for a counter: class VisitorDayTypeCounter(models.Model): visitType = models.CharField(max_length=60) visitDate = models.DateField('Visit Date') counter = models.IntegerField() When someone comes through, it will look for a row that matches the visitType and visitDate; if this row doesn't exist, it will be created with counter=0. Then we increment the counter and save. My concern is that this process is totally a race. Two requests could simultaneously check to see if the entity is there, and both of them could create it.

I want to monitor all the open windows under X11. Currently, I'm doing this as follows: Initially walking the whole tree by recursively calling XQueryTree from the root window Listening for substructure changes on the whole desktop: XSelectInput( display, root_window, SubstructureNotifyMask | PropertyChangeMask ) Handling all MapNotify, UnmapNotify and DestroyNotify events, updating my own list of windows in the process I'm mainly worried about point 1. During the recursion, XQueryTree will be called multiple times. Is there any way to ensure that the tree does not change in the meantime? In

I am reading the book Java Concurrency in Practice session 4.3.5 @ThreadSafe public class SafePoint{ @GuardedBy("this") private int x,y; private SafePoint (int [] a) { this (a[0], a[1]); } public SafePoint(SafePoint p) { this (p.get()); } public SafePoint(int x, int y){ this.x = x; this.y = y; } public synchronized int[] get(){ return new int[] {x,y}; } public synchronized void set(int x, int y){ this.x = x; this.y = y; } } I am not clear where It says The private constructor exists to avoid the race condition that would occur if the copy constructor were implemented as this (p.x, p.y); this