Hi, I'm seeing system occasionally hanging after "oom01" testcase from LTP triggers OOM. Here's a console log obtained from v4.4-8606 (shows oom, followed by blocked task messages, followed by me triggering sysrq-t): http://jan.stancek.eu/tmp/oom_hangs/oom_hang_v4.4-8606.txt http://jan.stancek.eu/tmp/oom_hangs/config-v4.4-8606.txt I'm running this patch on top, to trigger sysrq-t (system is in remote location): diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c index 36e2697..f1a27f3 100644 --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -77,6 +77,7 @@ #include <linux/string.h> #include <linux/netfilter_ipv4.h> #include <linux/slab.h> +#include <linux/sched.h> #include <net/snmp.h> #include <net/ip.h> #include <net/route.h> @@ -917,6 +918,10 @@ static bool icmp_echo(struct sk_buff *skb) icmp_param.data_len = skb->len; icmp_param.head_len = sizeof(struct icmphdr); icmp_reply(&icmp_param, skb); + if (icmp_param.data_len == 1025) { + printk("icmp_echo: %d\n", icmp_param.data_len); + show_state(); + } } /* should there be an ICMP stat for ignored echos? */ return true; oom01 testcase used to be single threaded, which however caused tests to run a long time on big boxes with 4+TB of RAM. So, to speed memory consumption we made it to consume memory in multiple threads. This was roughly the time kernels started hanging during OOM. I went back to try older longterm stable releases (3.10.94, 3.12.52), but I could reproduce problem here as well. So it seems that problem always existed, but only recent test change exposed it. I have couple bare metal systems where it triggers within couple hours. For example: 1x CPU Intel(R) Xeon(R) CPU E3-1285L with 16GB ram. It's not arch specific, it happens on ppc64 be/le lpar's or KVM guests too. My reproducer involves running LTP's oom01 testcase in loop. The core of test is alloc_mem(), which is a combination of mmap/mlock/madvice and touching all pages: https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/mem/lib/mem.c#L29 Regards, Jan -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>