mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-11-24 16:30:52 +07:00
a5c9b696ec
If a kthread happens to use get_user_pages() on an mm (as KSM does), there's a chance that it will end up trying to read in a swap page, then oops in grab_swap_token() because the kthread has no mm: GUP passes down the right mm, so grab_swap_token() ought to be using it. We have not identified a stronger case than KSM's daemon (not yet in mainline), but the issue must have come up before, since RHEL has included a fix for this for years (though a different fix, they just back out of grab_swap_token if current->mm is unset: which is what we first proposed, but using the right mm here seems more correct). Reported-by: Izik Eidus <ieidus@redhat.com> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk> Acked-by: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
78 lines
1.9 KiB
C
78 lines
1.9 KiB
C
/*
|
|
* mm/thrash.c
|
|
*
|
|
* Copyright (C) 2004, Red Hat, Inc.
|
|
* Copyright (C) 2004, Rik van Riel <riel@redhat.com>
|
|
* Released under the GPL, see the file COPYING for details.
|
|
*
|
|
* Simple token based thrashing protection, using the algorithm
|
|
* described in: http://www.cs.wm.edu/~sjiang/token.pdf
|
|
*
|
|
* Sep 2006, Ashwin Chaugule <ashwin.chaugule@celunite.com>
|
|
* Improved algorithm to pass token:
|
|
* Each task has a priority which is incremented if it contended
|
|
* for the token in an interval less than its previous attempt.
|
|
* If the token is acquired, that task's priority is boosted to prevent
|
|
* the token from bouncing around too often and to let the task make
|
|
* some progress in its execution.
|
|
*/
|
|
|
|
#include <linux/jiffies.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/swap.h>
|
|
|
|
static DEFINE_SPINLOCK(swap_token_lock);
|
|
struct mm_struct *swap_token_mm;
|
|
static unsigned int global_faults;
|
|
|
|
void grab_swap_token(struct mm_struct *mm)
|
|
{
|
|
int current_interval;
|
|
|
|
global_faults++;
|
|
|
|
current_interval = global_faults - mm->faultstamp;
|
|
|
|
if (!spin_trylock(&swap_token_lock))
|
|
return;
|
|
|
|
/* First come first served */
|
|
if (swap_token_mm == NULL) {
|
|
mm->token_priority = mm->token_priority + 2;
|
|
swap_token_mm = mm;
|
|
goto out;
|
|
}
|
|
|
|
if (mm != swap_token_mm) {
|
|
if (current_interval < mm->last_interval)
|
|
mm->token_priority++;
|
|
else {
|
|
if (likely(mm->token_priority > 0))
|
|
mm->token_priority--;
|
|
}
|
|
/* Check if we deserve the token */
|
|
if (mm->token_priority > swap_token_mm->token_priority) {
|
|
mm->token_priority += 2;
|
|
swap_token_mm = mm;
|
|
}
|
|
} else {
|
|
/* Token holder came in again! */
|
|
mm->token_priority += 2;
|
|
}
|
|
|
|
out:
|
|
mm->faultstamp = global_faults;
|
|
mm->last_interval = current_interval;
|
|
spin_unlock(&swap_token_lock);
|
|
}
|
|
|
|
/* Called on process exit. */
|
|
void __put_swap_token(struct mm_struct *mm)
|
|
{
|
|
spin_lock(&swap_token_lock);
|
|
if (likely(mm == swap_token_mm))
|
|
swap_token_mm = NULL;
|
|
spin_unlock(&swap_token_lock);
|
|
}
|