global kernel lock

Richard Gooch (rgooch@atnf.csiro.au)
Sat, 14 Nov 1998 02:08:25 +1100

Hi, all. I happened to be looking at some system calls (read(2) for
example) and I noticed that the global kernel lock is still being
grabbed. Looking further, I noticed that a context switch should
release the lock, so one process blocked reading a slow device should
not prevent another process from reading another device.

However, it looks like with an SMP machine that two processes can't
concurrently read, say, a regular file and a fast (non-sleeping)
device, since only one process can own the global kernel lock. I was a
little surprised at this, since I thought we'd pretty much gotten rid
of the global kernel lock in 2.1.x. Although, I have to admit I
haven't been paying close attention.

I have two simple questions:

- is my reading of the code correct

- does anyone have removing this on their ToDo for 2.3?

Regards,

Richard....

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