syzbot is sometimes getting mixed output like below due to concurrent printk(). Mitigate such output by using line-buffered printk() API.
Node 0 DMA: 1*4kB (U) 0*8kB 0*16kB 1*32kB syz-executor0: page allocation failure: order:0, mode:0x484020(GFP_ATOMIC|__GFP_COMP), nodemask=(null) (U) syz-executor0 cpuset= 2*64kB syz0 (U) mems_allowed=0 1*128kB CPU: 0 PID: 7592 Comm: syz-executor0 Not tainted 4.19.0-rc6+ #118 (U) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 1*256kB (U) Call Trace: 0*512kB <IRQ> 1*1024kB __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113 (U) 1*2048kB warn_alloc.cold.119+0xb7/0x1bd mm/page_alloc.c:3426 (M) Signed-off-by: Tetsuo Handa <[email protected]> Cc: Andrew Morton <[email protected]> --- mm/page_alloc.c | 32 +++++++++++++++++--------------- 1 file changed, 17 insertions(+), 15 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index a919ba5..4411d5a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4694,10 +4694,10 @@ unsigned long nr_free_pagecache_pages(void) return nr_free_zone_pages(gfp_zone(GFP_HIGHUSER_MOVABLE)); } -static inline void show_node(struct zone *zone) +static inline void show_node(struct zone *zone, struct printk_buffer *buf) { if (IS_ENABLED(CONFIG_NUMA)) - printk("Node %d ", zone_to_nid(zone)); + printk_buffered(buf, "Node %d ", zone_to_nid(zone)); } long si_mem_available(void) @@ -4814,7 +4814,7 @@ static bool show_mem_node_skip(unsigned int flags, int nid, nodemask_t *nodemask #define K(x) ((x) << (PAGE_SHIFT-10)) -static void show_migration_types(unsigned char type) +static void show_migration_types(unsigned char type, struct printk_buffer *buf) { static const char types[MIGRATE_TYPES] = { [MIGRATE_UNMOVABLE] = 'U', @@ -4838,7 +4838,7 @@ static void show_migration_types(unsigned char type) } *p = '\0'; - printk(KERN_CONT "(%s) ", tmp); + printk_buffered(buf, "(%s) ", tmp); } /* @@ -4852,6 +4852,7 @@ static void show_migration_types(unsigned char type) */ void show_free_areas(unsigned int filter, nodemask_t *nodemask) { + struct printk_buffer *buf = get_printk_buffer(); unsigned long free_pcp = 0; int cpu; struct zone *zone; @@ -4950,8 +4951,8 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask) for_each_online_cpu(cpu) free_pcp += per_cpu_ptr(zone->pageset, cpu)->pcp.count; - show_node(zone); - printk(KERN_CONT + show_node(zone, buf); + printk_buffered(buf, "%s" " free:%lukB" " min:%lukB" @@ -4993,10 +4994,10 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask) K(free_pcp), K(this_cpu_read(zone->pageset->pcp.count)), K(zone_page_state(zone, NR_FREE_CMA_PAGES))); - printk("lowmem_reserve[]:"); + printk_buffered(buf, "lowmem_reserve[]:"); for (i = 0; i < MAX_NR_ZONES; i++) - printk(KERN_CONT " %ld", zone->lowmem_reserve[i]); - printk(KERN_CONT "\n"); + printk_buffered(buf, " %ld", zone->lowmem_reserve[i]); + printk_buffered(buf, "\n"); } for_each_populated_zone(zone) { @@ -5006,8 +5007,8 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask) if (show_mem_node_skip(filter, zone_to_nid(zone), nodemask)) continue; - show_node(zone); - printk(KERN_CONT "%s: ", zone->name); + show_node(zone, buf); + printk_buffered(buf, "%s: ", zone->name); spin_lock_irqsave(&zone->lock, flags); for (order = 0; order < MAX_ORDER; order++) { @@ -5025,12 +5026,12 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask) } spin_unlock_irqrestore(&zone->lock, flags); for (order = 0; order < MAX_ORDER; order++) { - printk(KERN_CONT "%lu*%lukB ", - nr[order], K(1UL) << order); + printk_buffered(buf, "%lu*%lukB ", + nr[order], K(1UL) << order); if (nr[order]) - show_migration_types(types[order]); + show_migration_types(types[order], buf); } - printk(KERN_CONT "= %lukB\n", K(total)); + printk_buffered(buf, "= %lukB\n", K(total)); } hugetlb_show_meminfo(); @@ -5038,6 +5039,7 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask) printk("%ld total pagecache pages\n", global_node_page_state(NR_FILE_PAGES)); show_swap_cache_info(); + put_printk_buffer(buf); } static void zoneref_set_zone(struct zone *zone, struct zoneref *zoneref) -- 1.8.3.1
