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For example, a lock file might govern access to a set of related resources, such as several different files, directories, a group of disk partitions, or selected access to higher level protocols like servers or database connections. When using lock files, care must be taken to ensure that operations are atomic. To obtain a lock, the process ...
A memory-mapped file is a segment of virtual memory [1] that has been assigned a direct byte-for-byte correlation with some portion of a file or file-like resource. This resource is typically a file that is physically present on disk, but can also be a device, shared memory object, or other resource that an operating system can reference through a file descriptor.
Since multiple reader threads may hold the lock at once, this means that a writer thread may continue waiting for the lock while new reader threads are able to acquire the lock, even to the point where the writer may still be waiting after all of the readers which were holding the lock when it first attempted to acquire it have released the ...
Readers scale linearly by design. [10] [11] While write transactions are globally serialized via a mutex, read-only transactions operate in parallel, including in the presence of a write transaction. They are entirely wait free except for the first read-only transaction on a thread. Each thread reading from a database gains ownership of an ...
In this solution of the readers/writers problem, the first reader must lock the resource (shared file) if such is available. Once the file is locked from writers, it may be used by many subsequent readers without having them to re-lock it again. Before entering the critical section, every new reader must go through the entry section. However ...
The reader never blocks, but it may have to retry if a write is in progress; this speeds up the readers in the case where the data was not modified, since they do not have to acquire the lock as they would with a traditional read–write lock. Also, writers do not wait for readers, whereas with traditional read–write locks they do, leading to ...
atime record is not modified when file is read/accessed. Append-only a +a,-a: Writing to file only allowed in append mode. Immutable i +i,-i: Prevents any change to file's contents or metadata: file/directory cannot be written to, deleted, renamed, or hard-linked. No dump d +d,-d: File is skipped by the dump program: Secure deletion s +s,-s
In common region-locked DVDs (but not in RCE-DVDs), the region code is stored in the file "VIDEO_TS.IFO" (table "VMGM_MAT"), byte offsets 34 and 35. [13] The eight regions each correspond to a value which is a power of 2: Region 1 corresponds to 1 (2 0), Region 2 to 2 (2 1), Region 3 to 4 (2 2), and so on through Region 8, which corresponds to ...