On 11/15/24 11:45, Raghavendra K T wrote: > + Vlastimil > > Looks like he was unintentionally missed in CC. He has added Reviewed-by > to V1 Thanks, seems I did it for v1 when v2 was already sent, and without also cc linux-mm I didn't notice it was. > On 11/13/2024 3:51 PM, Adrian Huang wrote: >> From: Adrian Huang <ahuang12@xxxxxxxxxx> >> >> [Problem Description] >> When running the hackbench program of LTP, the following memory leak is >> reported by kmemleak. >> >> # /opt/ltp/testcases/bin/hackbench 20 thread 1000 >> Running with 20*40 (== 800) tasks. >> >> # dmesg | grep kmemleak >> ... >> kmemleak: 480 new suspected memory leaks (see /sys/kernel/debug/kmemleak) >> kmemleak: 665 new suspected memory leaks (see /sys/kernel/debug/kmemleak) >> >> # cat /sys/kernel/debug/kmemleak >> unreferenced object 0xffff888cd8ca2c40 (size 64): >> comm "hackbench", pid 17142, jiffies 4299780315 >> hex dump (first 32 bytes): >> ac 74 49 00 01 00 00 00 4c 84 49 00 01 00 00 00 .tI.....L.I..... >> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ >> backtrace (crc bff18fd4): >> [<ffffffff81419a89>] __kmalloc_cache_noprof+0x2f9/0x3f0 >> [<ffffffff8113f715>] task_numa_work+0x725/0xa00 >> [<ffffffff8110f878>] task_work_run+0x58/0x90 >> [<ffffffff81ddd9f8>] syscall_exit_to_user_mode+0x1c8/0x1e0 >> [<ffffffff81dd78d5>] do_syscall_64+0x85/0x150 >> [<ffffffff81e0012b>] entry_SYSCALL_64_after_hwframe+0x76/0x7e >> ... >> >> This issue can be consistently reproduced on three different servers: >> * a 448-core server >> * a 256-core server >> * a 192-core server >> >> [Root Cause] >> Since multiple threads are created by the hackbench program (along with >> the command argument 'thread'), a shared vma might be accessed by two or >> more cores simultaneously. When two or more cores observe that >> vma->numab_state is NULL at the same time, vma->numab_state will be >> overwritten. >> >> Although current code ensures that only one thread scans the VMAs in a >> single 'numa_scan_period', there might be a chance for another thread >> to enter in the next 'numa_scan_period' while we have not gotten till >> numab_state allocation [1]. >> >> Note that the command `/opt/ltp/testcases/bin/hackbench 50 process 1000` >> cannot the reproduce the issue. It is verified with 200+ test runs. >> >> [Solution] >> Use the cmpxchg atomic operation to ensure that only one thread executes >> the vma->numab_state assignment. >> >> [1] https://lore.kernel.org/lkml/1794be3c-358c-4cdc-a43d-a1f841d91ef7@xxxxxxx/ >> >> Fixes: ef6a22b70f6d ("sched/numa: apply the scan delay to every new vma") >> Reported-by: Jiwei Sun <sunjw10@xxxxxxxxxx> >> Signed-off-by: Adrian Huang <ahuang12@xxxxxxxxxx> >> Reviewed-by: Raghavendra K T <raghavendra.kt@xxxxxxx> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx> >> --- >> kernel/sched/fair.c | 12 +++++++++--- >> 1 file changed, 9 insertions(+), 3 deletions(-) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 3356315d7e64..7f99df294583 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -3399,10 +3399,16 @@ static void task_numa_work(struct callback_head *work) >> >> /* Initialise new per-VMA NUMAB state. */ >> if (!vma->numab_state) { >> - vma->numab_state = kzalloc(sizeof(struct vma_numab_state), >> - GFP_KERNEL); >> - if (!vma->numab_state) >> + struct vma_numab_state *ptr; >> + >> + ptr = kzalloc(sizeof(*ptr), GFP_KERNEL); >> + if (!ptr) >> + continue; >> + >> + if (cmpxchg(&vma->numab_state, NULL, ptr)) { >> + kfree(ptr); >> continue; >> + } >> >> vma->numab_state->start_scan_seq = mm->numa_scan_seq; >>
