Messages in this thread Patch in this message | | | From | David Howells <> | Subject | [PATCH] anti-cross-CPU printk/oops interleaving | Date | Fri, 04 Jul 2003 10:11:18 +0100 |
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Hi Linus,
This patch prevents an oops on one CPU being interleaved char-by-char with printks being performed on other CPUs, thus rendering them actually readable under those circumstances.
David
diff -ur linux-2.5.74/kernel/printk.c linux-2.5.74-auto/kernel/printk.c --- linux-2.5.74/kernel/printk.c 2003-07-03 15:37:24.000000000 +0100 +++ linux-2.5.74-auto/kernel/printk.c 2003-07-03 15:41:15.000000000 +0100 @@ -378,6 +378,9 @@ logged_chars++; } +/* cpu currently holding logbuf_lock */ +static volatile int printk_cpu = -1; + /* * This is printk. It can be called from any context. We want it to work. * @@ -400,8 +403,9 @@ static char printk_buf[1024]; static int log_level_unknown = 1; - if (oops_in_progress) { - /* If a crash is occurring, make sure we can't deadlock */ + if (oops_in_progress && printk_cpu == smp_processor_id()) { + /* If a crash is occurring during printk() on this CPU, + * make sure we can't deadlock */ spin_lock_init(&logbuf_lock); /* And make sure that we print immediately */ init_MUTEX(&console_sem); @@ -409,6 +413,7 @@ /* This stops the holder of console_sem just where we want him */ spin_lock_irqsave(&logbuf_lock, flags); + printk_cpu = smp_processor_id(); /* Emit the output into the temporary buffer */ va_start(args, fmt); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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