Hi, greg k-h During our testing with 4.4.73 we got soft lockup like:
NMI watchdog: BUG: soft lockup - CPU#2 stuck for 23s! [systemd-udevd:856] ... Call Trace: [<ffffffff8109d139>] vprintk_emit+0x319/0x4a0 [<ffffffff8112182d>] printk_emit+0x33/0x3b [<ffffffff812f9e9c>] ? simple_strtoull+0x2c/0x50 [<ffffffff8109d39a>] devkmsg_write+0xaa/0x100 [<ffffffff8109d2f0>] ? vprintk+0x30/0x30 [<ffffffff811915f2>] do_readv_writev+0x1c2/0x270 [<ffffffff8117899d>] ? kmem_cache_free+0x7d/0x1a0 [<ffffffff81191729>] vfs_writev+0x39/0x50 [<ffffffff8119240a>] SyS_writev+0x4a/0xd0 [<ffffffff8158bc97>] entry_SYSCALL_64_fastpath+0x12/0x6a Currently in 4.4 the console_unlock() called by vprintk_emit() is with preemption disabled, so the cond_resched is not working, and soft lockup appear if it take too much time on writing data into every console. We found the upstream patch: commit 6b97a20d3a79 printk: set may_schedule for some of console_trylock() callers which should have addressed this issue, but not included in the latest 4.4.78 stable yet, is there any plan on backport it in future? Regards, Michael Wang
