locking

问题 While I was reading about ReaderWriterLockSlim lock mechanism , There was this guy who suggested that Interlock Functions can be used for a finer locking Also, I found here another answer from Marc : ...Writes make their change to a cloned copy, then use Interlocked.CompareExchange to swap the reference (re-applying their change if another thread mutated the reference in the interim). Well , Currently all I know about Interlocked object , is that it is used (in a multithreaded environment) to

问题 While I was reading about ReaderWriterLockSlim lock mechanism , There was this guy who suggested that Interlock Functions can be used for a finer locking Also, I found here another answer from Marc : ...Writes make their change to a cloned copy, then use Interlocked.CompareExchange to swap the reference (re-applying their change if another thread mutated the reference in the interim). Well , Currently all I know about Interlocked object , is that it is used (in a multithreaded environment) to

问题 We have 10 Linux boxes that must run 100 different tasks each week. These computers work at these tasks mostly at night when we are at home. One of my coworkers is working on a project to optimize run time by automating the starting of the tasks with Python. His program is going to read a list of tasks, grab an open task, mark that task as in progress in the file, and then once the task is finished mark the task as complete in the file. The task files will be on our network mount. We realize

问题 We have 10 Linux boxes that must run 100 different tasks each week. These computers work at these tasks mostly at night when we are at home. One of my coworkers is working on a project to optimize run time by automating the starting of the tasks with Python. His program is going to read a list of tasks, grab an open task, mark that task as in progress in the file, and then once the task is finished mark the task as complete in the file. The task files will be on our network mount. We realize

问题 I have a x86 assembly code: unsigned int oldval; __asm__ __volatile__ ( "movl $1, %0 \n" "lock xaddl %0, (%1) \n" : "=a" (oldval) : "b" (n))l; return oldval; and I want to translate it into arm assembly. Is there any prefix in arm assembly that does the same thing as "lock" here? 回答1: I don't know ARM, but from glossing over the manual, the following should approximate your atomic exchange-and-add: foo: LDREX R1, [R0] ; R0 is "n", load linked ADD R2, R1, 1 ; R2 = R1 + 1 STREX R3, R2, [R0] ;

问题 I have a x86 assembly code: unsigned int oldval; __asm__ __volatile__ ( "movl $1, %0 \n" "lock xaddl %0, (%1) \n" : "=a" (oldval) : "b" (n))l; return oldval; and I want to translate it into arm assembly. Is there any prefix in arm assembly that does the same thing as "lock" here? 回答1: I don't know ARM, but from glossing over the manual, the following should approximate your atomic exchange-and-add: foo: LDREX R1, [R0] ; R0 is "n", load linked ADD R2, R1, 1 ; R2 = R1 + 1 STREX R3, R2, [R0] ;

问题 What is a scalable lock? And how is it different from a non-scalable lock? I first saw this term in the context of the TBB rw-lock, and couldn't decide which to use. In addition, is there any rw-lock that prioritizes readers over writers? 回答1: There is no formal definition of the term "scalable lock" or "non-scalable lock". What it's meant to imply is that some locking algorithms, techniques or implementations perform reasonably well even when there is a lot of contention for the lock, and

问题 I have a write method that is supposed to safely write data to a file. // The current file I am writing to. FileOutputStream file = null; ... // Synchronized version. private void write(byte[] bytes) { if (file != null && file.getChannel() != null) { try { boolean written = false; do { try { // Lock it! FileLock lock = file.getChannel().lock(); try { // Write the bytes. file.write(bytes); written = true; } finally { // Release the lock. lock.release(); } } catch (OverlappingFileLockException

问题 How would I validate that a jpg file is a valid image file. We are having files written to a directory using FTP, but we seem to be picking up the file before it has finished writing it, creating invalid images. I need to be able to identify when it is no longer being written to. Any ideas? 回答1: Easiest way might just be to write the file to a temporary directory and then move it to the real directory after the write is finished. Or you could check here. JPEG::Error [arguments: none] If the

问题 When SQL Server Books online says that "Shared (S) locks on a resource are released as soon as the read operation completes , unless the transaction isolation level is set to repeatable read or higher, or a locking hint is used to retain the shared (S) locks for the duration of the transaction." Assuming we're talking about a row-level lock, with no explicit transaction, at default isolation level (Read Committed), what does " read operation " refer to? The reading of a single row of data?