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Subject[PATCH] nommu: yield CPU periodically while disposing large VM
Date
Depending on processor speed, page size, and the amount of memory a process
is allowed to amass, cleanup of a large VM may freeze the system for many
seconds. This can result in a watchdog timeout.

Make sure other tasks receive some service when cleaning up large VMs.

Signed-off-by: Steven J. Magnani <steve@digidescorp.com>
---
diff -uprN a/mm/nommu.c b/mm/nommu.c
--- a/mm/nommu.c 2010-10-21 07:42:23.000000000 -0500
+++ b/mm/nommu.c 2010-10-21 07:46:50.000000000 -0500
@@ -1656,6 +1656,7 @@ SYSCALL_DEFINE2(munmap, unsigned long, a
void exit_mmap(struct mm_struct *mm)
{
struct vm_area_struct *vma;
+ unsigned long next_yield = jiffies + HZ;

if (!mm)
return;
@@ -1668,6 +1669,11 @@ void exit_mmap(struct mm_struct *mm)
mm->mmap = vma->vm_next;
delete_vma_from_mm(vma);
delete_vma(mm, vma);
+ /* Yield periodically to prevent watchdog timeout */
+ if (time_after(jiffies, next_yield)) {
+ cond_resched();
+ next_yield = jiffies + HZ;
+ }
}

kleave("");


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