Re: Threads reading a file at the same time

Knute Johnson <>
Fri, 30 Jul 2010 09:21:37 -0700
On 7/29/2010 9:35 PM, Boris Punk wrote:

"Arne Vajh?j"<> wrote in message

On 29-07-2010 22:58, Boris Punk wrote:

I'm not sure about this one. The basic IDE hard drive hasn't got the
capability to read from two disk locations at the same time has it?
SSD drives may have.

This lock is stating that multiple reads are ok, but just one write at a
time is ok:

How can that be? Imagine Thread A calling seek on the disk, then Thread B
calling seek. Thread A then reads from B's location surely?

The ReadWriteLock is not related to the actual disk IO - it only
coordinates between two or more threads.


Fair enough - I was just read somewhere someone tried using it for a disk IO

That is a common usage for RWL. The reading threads can be blocked when
a write is about to occur. The actual read/write to the disk is another
matter altogether. Caching and other things can affect that as well.


Knute Johnson
email s/nospam/knute2010/

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