Concurrent read/writes on the same file

[HARAWAT.IN.ORACLE.COM]

In FreeBSD the vn_read function looks like this 
 
lock the vnode 
do the actual read 
unlock the vnode 
 
So it means that one read/write will execute in the kernel at one point of 
time, the second read/write will block while trying to lock the vnode. Is the 
same algo used in Linux also. Is the same algo used for the Raw Devices as 
well. 
 
 
Thanks 
Harish