5.4-stable review patch. If anyone has any objections, please let me know.
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From: Gerald Schaefer gerald.schaefer@linux.ibm.com
[ 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: Gerald Schaefer gerald.schaefer@linux.ibm.com Reviewed-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/mm/cmm.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/arch/s390/mm/cmm.c b/arch/s390/mm/cmm.c index a51c892f14f3e..756aefbd05249 100644 --- a/arch/s390/mm/cmm.c +++ b/arch/s390/mm/cmm.c @@ -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) {