Messages in this thread | | | Date | Tue, 2 Jun 2015 17:25:58 +0600 | Subject | Re: [PATCH v8 0/3] x86/earlyprintk: setup serial earlyprintk as early as possible | From | Alexander Kuleshov <> |
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2015-05-29 22:55 GMT+06:00 Borislav Petkov <bp@suse.de>: > > You can boot with "ignore_loglevel" to see that message. Provided > ignore_loglevel is even parsed that early. >
But ignore_loglevel is early_param too...
> > Yes, I meant a testing patch which is used only for testing and which > issues a bunch of early_printk() calls. >
Maybe I just remove 'if' clause and just leave:
early_printk("Early printk is initialized\n");
In the arch/x86/kernel/head{32,64}.c? Call of the early_printk is safe here, even earlyprintk is not enabled and it must be good for testing this patchset.
> But, before you do that, your patchset has more problems. Booting in > qemu+kvm gives this: > > early console in setup code > early console in decompress_kernel > > Decompressing Linux... Parsing ELF... done. > Booting the kernel. > [ 0.000000] bootconsole [earlyser0] enabled > [ 0.000000] ERROR: earlyprintk= earlyser already used > ^^^^^^
Yes, thanks. This is because we go though a buffer in a loop and after the earlyprintk=ttyS0, it finds console=ttyS0. So, I think we can add additional check, something like this:
if (!strncmp(buf, "serial", 6) && early_serial_console.index == -1) { ... ... ... }
and for the "ttyS...". Just tested it and it works without "ERROR: earlyprintk= earlyser already used".
> > [ 0.000000] per task-struct memory footprint: 2688 bytes > [ 0.000000] WARNING: lockdep init error! lock-(console_sem).lock was acquiredbefore lockdep_init > [ 0.000000] Call stack leading to lockdep invocation was: > [ 0.000000] [<ffffffff81013f0f>] save_stack_trace+0x2f/0x50 > [ 0.000000] [<ffffffff810a364c>] __lock_acquire+0xa2c/0xf00 > [ 0.000000] [<ffffffff810a440b>] lock_acquire+0xdb/0x2b0 > [ 0.000000] [<ffffffff81676b33>] _raw_spin_lock_irqsave+0x53/0x90 > [ 0.000000] [<ffffffff8109b146>] down+0x16/0x50 > [ 0.000000] [<ffffffff810b4d49>] console_lock+0x19/0x60 > [ 0.000000] [<ffffffff810b78e6>] register_console+0x116/0x350 > [ 0.000000] [<ffffffff81c36162>] setup_early_printk+0x165/0x467 > [ 0.000000] [<ffffffff81c364ba>] setup_early_serial_console+0x56/0x58 > [ 0.000000] [<ffffffff81c24565>] x86_64_start_kernel+0xce/0x110 > [ 0.000000] [<ffffffffffffffff>] 0xffffffffffffffff > [ 0.000000] ------------------------ > > This last one shows that you'd need to look into lockdep first. It also > shows that early boot order is pretty fragile so one has to be very > careful when changing stuff there. >
What if I add call of the lockdep_init before the setup_early_serial_console? It must be safe because there is check in the lockdep_init:
if (lockdep_initialized) return;
and some architectures (powerpc, microblaze, s390) already do it in the same way.
What do you think about it?
Thank you.
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