On Fri, Feb 29, 2008 at 1:34 AM, Peter Teoh <htmldeveloper@xxxxxxxxx> wrote: > Sorry this part really puzzled me.... > > On Sat, Feb 9, 2008 at 8:10 AM, Rene Herman <rene.herman@xxxxxxxxxxxx> wrote: > > In the CPU's ALU. inode->i_size is a 64_bit integer, and access to it is > > atomic on 64-bit. On a 32-bit arch though, a 64-bit load will be split in > > two 32-bit ones where you can get an incoherent value if you're interrupted > > between getting the low and the high 32-bit. > > > > Rene. > > > I understood what u are saying, as i_size is loff_t, and loff_t is > defined as "long long". But the fact is this, of the thousands of > assembly instructions in the kernel, in between any two, it can always > be interrupted, so long as u ensure that the interrupt handler ensure > that all the registers that it modified has been restored back to its > original value upon returning. So I don't quite understand why it > cannot be interrupted between the upper and lower half of the 32bit > processing. Interrupts are used for many things. What if a timer interrupt occurs and it changes the current task? Then a different task can change the variable before control is resumed in the original task. I hope this explains your question. Vegard -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
