The patch titled Subject: mm: memcontrol: make per-cpu charge cache IRQ-safe for socket accounting has been removed from the -mm tree. Its filename was mm-memcontrol-make-per-cpu-charge-cache-irq-safe-for-socket-accounting.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Johannes Weiner <jweiner@xxxxxx> Subject: mm: memcontrol: make per-cpu charge cache IRQ-safe for socket accounting During cgroup2 rollout into production, we started encountering css refcount underflows and css access crashes in the memory controller. Splitting the heavily shared css reference counter into logical users narrowed the imbalance down to the cgroup2 socket memory accounting. The problem turns out to be the per-cpu charge cache. Cgroup1 had a separate socket counter, but the new cgroup2 socket accounting goes through the common charge path that uses a shared per-cpu cache for all memory that is being tracked. Those caches are safe against scheduling preemption, but not against interrupts - such as the newly added packet receive path. When cache draining is interrupted by network RX taking pages out of the cache, the resuming drain operation will put references of in-use pages, thus causing the imbalance. Disable IRQs during all per-cpu charge cache operations. Fixes: f7e1cb6ec51b ("mm: memcontrol: account socket memory in unified hierarchy memory controller") Link: http://lkml.kernel.org/r/20160914194846.11153-1-hannes@xxxxxxxxxxx Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> Acked-by: Tejun Heo <tj@xxxxxxxxxx> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxx> Cc: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> [4.5+] Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 31 ++++++++++++++++++++++--------- 1 file changed, 22 insertions(+), 9 deletions(-) diff -puN mm/memcontrol.c~mm-memcontrol-make-per-cpu-charge-cache-irq-safe-for-socket-accounting mm/memcontrol.c --- a/mm/memcontrol.c~mm-memcontrol-make-per-cpu-charge-cache-irq-safe-for-socket-accounting +++ a/mm/memcontrol.c @@ -1740,17 +1740,22 @@ static DEFINE_MUTEX(percpu_charge_mutex) static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages) { struct memcg_stock_pcp *stock; + unsigned long flags; bool ret = false; if (nr_pages > CHARGE_BATCH) return ret; - stock = &get_cpu_var(memcg_stock); + local_irq_save(flags); + + stock = this_cpu_ptr(&memcg_stock); if (memcg == stock->cached && stock->nr_pages >= nr_pages) { stock->nr_pages -= nr_pages; ret = true; } - put_cpu_var(memcg_stock); + + local_irq_restore(flags); + return ret; } @@ -1771,15 +1776,18 @@ static void drain_stock(struct memcg_sto stock->cached = NULL; } -/* - * This must be called under preempt disabled or must be called by - * a thread which is pinned to local cpu. - */ static void drain_local_stock(struct work_struct *dummy) { - struct memcg_stock_pcp *stock = this_cpu_ptr(&memcg_stock); + struct memcg_stock_pcp *stock; + unsigned long flags; + + local_irq_save(flags); + + stock = this_cpu_ptr(&memcg_stock); drain_stock(stock); clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags); + + local_irq_restore(flags); } /* @@ -1788,14 +1796,19 @@ static void drain_local_stock(struct wor */ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) { - struct memcg_stock_pcp *stock = &get_cpu_var(memcg_stock); + struct memcg_stock_pcp *stock; + unsigned long flags; + + local_irq_save(flags); + stock = this_cpu_ptr(&memcg_stock); if (stock->cached != memcg) { /* reset if necessary */ drain_stock(stock); stock->cached = memcg; } stock->nr_pages += nr_pages; - put_cpu_var(memcg_stock); + + local_irq_restore(flags); } /* _ Patches currently in -mm which might be from jweiner@xxxxxx are -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html