race-condition

问题 I'm writing a program that uses a sqlite3 database file to store its data. If I open a database file with sqlite3_open_v2(filename, &db, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, NULL) the database file is created if it does not exist. How can I find out if the database file existed prior to opening it? The sqlite3 shell uses code like this: /* Go ahead and open the database file if it already exists. If the ** file does not exist, delay opening it. This prevents empty database ** files

问题 I've heard about many application developers having a bit of trouble in regards to race conditions in database processing. A typical example goes something like this: User 1 selects a field, say, numStock, which is 3 User 2 also selects numStock, which is still 3 User 1 decrements numStock (in the app), and sets it to 2 in the database. User 2 also decrements numStock (in the app), and sets it to 2 in the database. In this example, the numStock field should have become 1, but it was set to 2

问题 In MS SQL Server, I'm using a global temp table to store session related information passed by the client and then I use that information inside triggers. Since the same global temp table can be used in different sessions and it may or may not exist when I want to write into it (depending on whether all the previous sessions which used it before are closed), I'm doing a check for the global temp table existence based on which I create before I write into it. IF OBJECT_ID('tempdb..##VTT

问题 I am attempting to track events when links are clicked on my site in a method similar to the following. <a href="/example" class="track">Example</a> <script type="text/javascript"> jQuery(function($) { // track clicks on all anchor tags that require it $('a.track').live('click', function(e) { // send an AJAX request to our event tracking URL for the server to track it $.get('/events/track', { url: $(this).attr('href'), text: $(this).text() }); }); }); </script> The problem that I'm having is

问题 void undefined_behaviour_with_double_checked_locking() { if(!resource_ptr) #1 { std::lock_guard<std::mutex> lk(resource_mutex); #2 if(!resource_ptr) #3 { resource_ptr.reset(new some_resource); #4 } } resource_ptr->do_something(); #5 } if a thread sees the pointer written by another thread, it might not see the newly-created instance of some_resource, resulting in the call to do_something() operating on incorrect values. This is an example of the type of race condition defined as a data race

问题 I have a component structure like this <A> <B> <C/> <C/> </B> <D> <E/> <E/> </D> </A> Idea is that actions on components in block E are processed by a function of component A to state of A and than passed down to B and C as props. I know, that better way was to use Flux, pubsub-js or other Store-message system, but hope if someone can explain why correct to the best of my understanding solution doesn't work. Calling this function of component A simalteneously from multiple instances of

问题 In a linux device driver, creating sysfs attributes in probe is way too racy--specifically, it experiences a race condition with userspace. The recommended workaround is to add your attributes to various default attribute groups so they can be automatically created before probe. For a device driver, struct device_driver contains const struct attribute_group **groups for this purpose. However, struct attribute_group only got a field for binary attributes in Linux 3.11. With older kernels

问题 In APUE section 8.3 fork function , about file sharing between parent and child processes, It said: It is important that the parent and the child share the same file offset. And in section 8.9 Race Conditions , there is a example: both parent and child write to a file which is opened before invoking fork function. The program contains a race condition, because the output depends on the order in which the processes are run by the kernel and for how long each process runs. But in my test code,

问题 I'm trying to find the maximum weight of about 6.1 billion (custom) items and I would like to do this with parallel processing. For my particular application there are better algorithms that don't require my iterating over 6.1 billion items, but the textbook that explains them is over my head and my boss wants this done in 4 days. I figured I have a better shot with my company's fancy server and parallel processing. However, everything I know about parallel processing comes from reading the

问题 Greetings, I've been studying javascript, nodejs. And I don't understand how the concurrency issues are avoided in javascript. Lets say I'm working on a object var bigObject = new BigObject(); and I have a setTimer(function(){ workOnBigOjbect...} ) that will also do work on bigOjbect . If I have disk IO being written into bigObject , and a timer object working on bigObject , and regularly code reading from bigObject , how are concurrency issues avoided? In a regular language, I would use a