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Commit a12b82d7 authored by Gerald Schaefer's avatar Gerald Schaefer Committed by Greg Kroah-Hartman
Browse files

s390/mm: Add cond_resched() to cmm_alloc/free_pages() 



[ Upstream commit 131b8db78558120f58c5dc745ea9655f6b854162 ]

Adding/removing large amount of pages at once to/from the CMM balloon
can result in rcu_sched stalls or workqueue lockups, because of busy
looping w/o cond_resched().

Prevent this by adding a cond_resched(). cmm_free_pages() holds a
spin_lock while looping, so it cannot be added directly to the existing
loop. Instead, introduce a wrapper function that operates on maximum 256
pages at once, and add it there.

Signed-off-by: default avatarGerald Schaefer <gerald.schaefer@linux.ibm.com>
Reviewed-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent f559306a

arch/s390/mm/cmm.c

+17 −1
Original line number Diff line number Diff line
@@ -98,11 +98,12 @@ static long cmm_alloc_pages(long nr, long *counter, 
		(*counter)++;

		spin_unlock(&cmm_lock);

		nr--;

		cond_resched();

	}

	return nr;

}



static long cmm_free_pages(long nr, long *counter, struct cmm_page_array **list)

static long __cmm_free_pages(long nr, long *counter, struct cmm_page_array **list)

{

	struct cmm_page_array *pa;

	unsigned long addr;
@@ -126,6 +127,21 @@ static long cmm_free_pages(long nr, long *counter, struct cmm_page_array **list) 
	return nr;

}



static long cmm_free_pages(long nr, long *counter, struct cmm_page_array **list)

{

	long inc = 0;



	while (nr) {

		inc = min(256L, nr);

		nr -= inc;

		inc = __cmm_free_pages(inc, counter, list);

		if (inc)

			break;

		cond_resched();

	}

	return nr + inc;

}



static int cmm_oom_notify(struct notifier_block *self,

			  unsigned long dummy, void *parm)

{