Messages in this thread Patch in this message | | | From | "Shilimkar, Santosh" <> | Date | Tue, 29 Jun 2010 14:22:26 +0530 | Subject | Additional fix : (was [v2]printk: fix delayed messages from CPU hotplug events) |
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Hi,
I have faced similar issue as what is being described in below with latest kernel.
------------------------------------------------ https://patchwork.kernel.org/patch/103347/
When a secondary CPU is being brought up, it is not uncommon for printk() to be invoked when cpu_online(smp_processor_id()) == 0. The case that I witnessed personally was on MIPS:
http://lkml.org/lkml/2010/5/30/4
If (can_use_console() == 0), printk() will spool its output to log_buf and it will be visible in "dmesg", but that output will NOT be echoed to the console until somebody calls release_console_sem() from a CPU that is online. Therefore, the boot time messages from the new CPU can get stuck in "limbo" for a long time, and might suddenly appear on the screen when a completely unrelated event (e.g. "eth0: link is down") occurs.
This patch modifies the console code so that any pending messages are automatically flushed out to the console whenever a CPU hotplug operation completes successfully or aborts.
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Above patch fixes only half of the problem. I mean the cpu online path prints are coming on the console.
But similar problem also exist if there are prints in the cpu offline path. I got that fixed by adding below patch on top of you patch. diff --git a/kernel/printk.c b/kernel/printk.c index d370b74..f4d7352 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -982,6 +982,9 @@ static int __cpuinit console_cpu_notify(struct notifier_bloc switch (action) { case CPU_ONLINE: case CPU_UP_CANCELED: + case CPU_DEAD: + case CPU_DYING: + case CPU_DOWN_FAILED: if (try_acquire_console_sem() == 0) release_console_sem(); }
Regards Santosh
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