Sergey Senozhatsky wrote: > On (12/22/16 23:01), Tetsuo Handa wrote: > > > On (12/22/16 19:27), Tetsuo Handa wrote: > > > > Thank you. I tried "[PATCHv6 0/7] printk: use printk_safe to handle printk() > > > > recursive calls" at https://lkml.org/lkml/2016/12/21/232 on top of linux.git > > > > as of commit 52bce91165e5f2db "splice: reinstate SIGPIPE/EPIPE handling", but > > > > it turned out that your patch set does not solve this problem. > > > > > > > > I was assuming that sending to consoles from printk() is offloaded to a kernel > > > > thread dedicated for that purpose, but your patch set does not do it. > > > > > > sorry, seems that I didn't deliver the information properly. > > > > > > https://gitlab.com/senozhatsky/linux-next-ss/commits/printk-safe-deferred > > > > > > there are 2 patch sets. the first one is printk-safe. the second one > > > is async printk. > > > > > > 9 patches in total (as of now). > > > > > > can you access it? > > > > "404 The page you're looking for could not be found." > > > > Anonymous access not supported? > > oops... hm, dunno, it says > > : Visibility Level (?) > : > : Public > : The project can be cloned without any authentication. > > I'll switch to github then may be. > > attached 9 patches. > > NOTE: not the final version. > > > -ss I tried these 9 patches. Generally OK. Although there is still "schedule_timeout_killable() lockup with oom_lock held" problem, async-printk patches help avoiding "printk() lockup with oom_lock held" problem. Thank you. Three comments from me. (1) Messages from e.g. SysRq-b is not waited for sent to consoles. "SysRq : Resetting" line is needed as a note that I gave up waiting. (2) Messages from e.g. SysRq-t should be sent to consoles synchronously? "echo t > /proc/sysrq-trigger" case can use asynchronous printing. But since ALT-SysRq-T sequence from keyboard may be used when scheduler is not responding, it might be better to use synchronous printing. (Or define a magic key sequence to toggle synchronous/asynchronous?) (3) I got below warning. (Though not reproducible.) If fb_flashcursor() called console_trylock(), console_may_schedule is set to 1? ---------------------------------------- [ OK [ 255.862188] audit: type=1131 audit(1482733112.662:148): pid=1 uid=0 auid=4294967295 ses=4294967295 msg='unit=systemd-tmpfiles-setup-dev comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success' ] Stopped Create Static Device Nodes in /dev. [ 255.871468] BUG: sleeping function called from invalid context at kernel/printk/printk.c:2325 [ 255.871469] in_atomic(): 1, irqs_disabled(): 1, pid: 10079, name: plymouthd [ 255.871469] 6 locks held by plymouthd/10079: [ 255.871470] #0: (&tty->ldisc_sem){++++.+}, at: [<ffffffff817413e2>] ldsem_down_read+0x32/0x40 [ 255.871472] #1: (&tty->atomic_write_lock){+.+.+.}, at: [<ffffffff81424309>] tty_write_lock+0x19/0x50 [ 255.871474] #2: (&tty->termios_rwsem){++++..}, at: [<ffffffff81429d59>] n_tty_write+0x99/0x470 [ 255.871475] #3: (&ldata->output_lock){+.+...}, at: [<ffffffff81429df0>] n_tty_write+0x130/0x470 [ 255.871477] #4: (console_lock){+.+.+.}, at: [<ffffffff8110616e>] console_unlock+0x33e/0x6b0 [ 255.871479] #5: (printing_lock){......}, at: [<ffffffff8143baf5>] vt_console_print+0x75/0x3d0 [ 255.871481] irq event stamp: 15244 [ 255.871481] hardirqs last enabled at (15243): [<ffffffff81105011>] __down_trylock_console_sem+0x91/0xa0 [ 255.871482] hardirqs last disabled at (15244): [<ffffffff81105ea4>] console_unlock+0x74/0x6b0 [ 255.871482] softirqs last enabled at (14968): [<ffffffff81096394>] __do_softirq+0x344/0x580 [ 255.871482] softirqs last disabled at (14963): [<ffffffff810968d3>] irq_exit+0xe3/0x120 [ 255.871483] CPU: 0 PID: 10079 Comm: plymouthd Not tainted 4.9.0-next-20161224+ #12 [ 255.871483] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/31/2013 [ 255.871484] Call Trace: [ 255.871484] dump_stack+0x85/0xc9 [ 255.871485] ___might_sleep+0x14a/0x250 [ 255.871485] console_conditional_schedule+0x22/0x30 [ 255.871485] fbcon_redraw.isra.24+0xa3/0x1d0 [ 255.871486] ? fbcon_cursor+0x151/0x1c0 [ 255.871486] fbcon_scroll+0x11d/0xcb0 [ 255.871487] con_scroll+0x160/0x170 [ 255.871487] lf+0x9c/0xb0 [ 255.871487] vt_console_print+0x2b7/0x3d0 [ 255.871488] console_unlock+0x457/0x6b0 [ 255.871488] do_con_write.part.19+0x737/0x9e0 [ 255.871489] ? mark_held_locks+0x71/0x90 [ 255.871489] con_write+0x57/0x60 [ 255.871489] n_tty_write+0x1bf/0x470 [ 255.871490] ? prepare_to_wait_event+0x110/0x110 [ 255.871490] tty_write+0x157/0x2d0 [ 255.871491] ? n_tty_open+0xd0/0xd0 [ 255.871491] __vfs_write+0x32/0x140 [ 255.871491] ? trace_hardirqs_on+0xd/0x10 [ 255.871492] ? __audit_syscall_entry+0xaa/0xf0 [ 255.871492] vfs_write+0xc2/0x1f0 [ 255.871493] ? syscall_trace_enter+0x1cb/0x3e0 [ 255.871493] SyS_write+0x53/0xc0 [ 255.871493] do_syscall_64+0x67/0x1f0 [ 255.871494] entry_SYSCALL64_slow_path+0x25/0x25 [ 255.871494] RIP: 0033:0x7fb74cf8fc60 [ 255.871495] RSP: 002b:00007ffcaab3fe88 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 [ 255.871495] RAX: ffffffffffffffda RBX: 000055d3acaf7160 RCX: 00007fb74cf8fc60 [ 255.871496] RDX: 000000000000003f RSI: 000055d3acafd090 RDI: 0000000000000009 [ 255.871496] RBP: 000055d3acafc440 R08: 0000000000000070 R09: 0000000000000000 [ 255.871497] R10: 000000000000003f R11: 0000000000000246 R12: 000055d3acafc330 [ 255.871497] R13: 000000000000003f R14: 00007ffcaab3ffb0 R15: 0000000000000000 Stopping Create Static Device Nodes in /dev... ---------------------------------------- # ./scripts/faddr2line vmlinux console_unlock+0x74/0x6b0 console_unlock+0x74/0x6b0: console_unlock at kernel/printk/printk.c:2228 # ./scripts/faddr2line vmlinux console_unlock+0x457/0x6b0 console_unlock+0x457/0x6b0: call_console_drivers at kernel/printk/printk.c:1613 (inlined by) console_unlock at kernel/printk/printk.c:2277 # ./scripts/faddr2line vmlinux vt_console_print+0x2b7/0x3d0 vt_console_print+0x2b7/0x3d0: cr at drivers/tty/vt/vt.c:1137 (inlined by) vt_console_print at drivers/tty/vt/vt.c:2598 # ./scripts/faddr2line vmlinux lf+0x9c/0xb0 lf+0x9c/0xb0: lf at drivers/tty/vt/vt.c:1112 # ./scripts/faddr2line vmlinux con_scroll+0x160/0x170 con_scroll+0x160/0x170: con_scroll at drivers/tty/vt/vt.c:327 (discriminator 1) # ./scripts/faddr2line vmlinux fbcon_scroll+0x11d/0xcb0 fbcon_scroll+0x11d/0xcb0: fbcon_scroll at drivers/video/console/fbcon.c:1898 # ./scripts/faddr2line vmlinux fbcon_cursor+0x151/0x1c0 fbcon_cursor+0x151/0x1c0: fbcon_cursor at drivers/video/console/fbcon.c:1331 # ./scripts/faddr2line vmlinux fbcon_redraw.isra.24+0xa3/0x1d0 fbcon_redraw.isra.24+0xa3/0x1d0: fbcon_redraw at drivers/video/console/fbcon.c:1756 # ./scripts/faddr2line vmlinux console_conditional_schedule+0x22/0x30 console_conditional_schedule+0x22/0x30: console_conditional_schedule at kernel/printk/printk.c:2325 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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