On Mon, 2002-01-28 at 11:53, Geert Uytterhoeven wrote:
> On Mon, 28 Jan 2002, Phil Thompson wrote:
> > - USER_PTRS_PER_PGD is defined as TASK_SIZE/PGDIR_SIZE. However,
> > because, TASK_SIZE is actually defined as one less that the maximum task
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > size there is a rounding error that means that USER_PTRS_PER_PGD works
> ^^^^
> > out at 511 rather than 512. This means that entries 511 and 1023 of
> > swapper_pg_dir don't get initialised.
> >
> > The corresponding mips64 code has only the first call to pgd_init() and
> > each implementation of pgd_init() initialises PTRS_PER_PGD entries,
> > where PTRS_PER_PGD is simple defined as 1024.
> >
> > The attached patch applies the mips64 approach to the mips code.
> >
> > Should USER_PTRS_PER_PGD be defined as (TASK_SIZE/PGDIR_SIZE) + 1?
>
> You mean ((TASK_SIZE)+1)/PGDIR_SIZE?
Or how about:
#define USER_PTRS_PER_PGD ((TASK_SIZE-1)/PGDIR_SIZE + 1)
The above patch fixes a rather serious memory leak. When a parent
process forks a large number of children and then it exits before the
children exit, we lose one page per child. I was able to narrow down the
problem and reproduce it with the attached program. Ralf has the fix,
but was examining related issues before applying the patch.
Pete
#include <signal.h>
#define NUM_TSK 200
int main()
{
int i, lastp;
int pids[NUM_TSK];
printf("mypid %d\n", getpid());
for (i=0; i<NUM_TSK; i++) {
switch (pids[i] = fork()) {
case -1:
printf("fork failed, lastp %d\n", lastp);
goto killall;
case 0:
sleep(4);
return 0;
break;
default:
lastp = i;
}
}
killall:
return 0;
}
