From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleksandr Natalenko Subject: WARN_ON() in netconsole with PREEMPT_RT Date: Sun, 11 Nov 2018 20:13:40 +0100 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Cc: Steven Rostedt , Sebastian Andrzej Siewior , Thomas Gleixner , Eric Dumazet , Dave Jones , netdev@vger.kernel.org, linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org To: "David S. Miller" Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org Hi. I was just curious about PREEMPT_RT and decided to give it a (small) shot on my laptop. As a safety measure, I've enabled netconsole to catch all the weird stuff that can pop up, and immediately it indeed did… in the netconsole code itself (irony): === [ 64.018949] WARNING: CPU: 0 PID: 1204 at net/core/netpoll.c:372 netpoll_send_udp+0x3e8/0x3ef … [ 64.019057] CPU: 0 PID: 1204 Comm: bash Not tainted 4.19.0-ig1 #1 [ 64.019058] Hardware name: Dell Inc. Vostro 3360/0F5DWF, BIOS A18 09/25/2013 [ 64.019063] RIP: 0010:netpoll_send_udp+0x3e8/0x3ef [ 64.019066] Code: dd ff ff 41 ba 86 dd ff ff 49 2b 96 d0 00 00 00 66 41 89 96 c6 00 00 00 66 44 89 48 0c 66 45 89 96 c0 00 00 00 e9 93 fe ff ff <0f> 0b e9 40 fc ff ff 0f 1f 44 00 00 53 0f b7 57 42 48 89 fb 48 8b [ 64.019068] RSP: 0018:ffffaa6743f87c98 EFLAGS: 00010202 [ 64.019070] RAX: 0000000000000292 RBX: 0000000000000014 RCX: 0000000000000028 [ 64.019072] RDX: 0000000000000014 RSI: ffffffffb1e6a300 RDI: ffff95973d905668 [ 64.019073] RBP: ffffaa6743f87cd8 R08: ffffffffc11f6ba0 R09: 0000000000000000 [ 64.019075] R10: 0000000000000008 R11: 0000000000000000 R12: 00000000000003e8 [ 64.019076] R13: ffff95973d905668 R14: 0000000000000014 R15: ffff95973d905668 [ 64.019079] FS: 00007f2f8b809b80(0000) GS:ffff95976f000000(0000) knlGS:0000000000000000 [ 64.019081] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 64.019083] CR2: 000055b8e126fbc8 CR3: 0000000415440006 CR4: 00000000001606f0 [ 64.019084] Call Trace: [ 64.019098] write_msg+0xd1/0xe0 [netconsole] [ 64.019107] console_unlock.part.6+0x55b/0x5a0 [ 64.019115] ? _raw_spin_unlock_irqrestore+0x20/0x60 [ 64.019120] vprintk_emit+0x16a/0x1a0 [ 64.019125] printk_emit+0x44/0x5b [ 64.019130] ? _raw_spin_trylock+0x13/0x80 [ 64.019134] devkmsg_write.cold.16+0x21/0x4e [ 64.019140] __vfs_write+0x136/0x1a0 [ 64.019145] vfs_write+0xa9/0x1a0 [ 64.019149] ksys_write+0x52/0xc0 [ 64.019156] do_syscall_64+0x5b/0x170 [ 64.019160] entry_SYSCALL_64_after_hwframe+0x44/0xa9 … === This is a v4.19.1-rt3-based kernel. The WARN_ON() is: 362 void netpoll_send_udp(struct netpoll *np, const char *msg, int len) 363 { … 372 WARN_ON_ONCE(!irqs_disabled()); … If that matters, I have "threadirqs" passed to the kernel. Netconsole seems to work even after this warning. Is this OK/expected? Thanks. -- Oleksandr Natalenko (post-factum)