On Sat, 1 Jul 2000 18:31:12 -0700 (PDT),
Chris Lattner <sabre@skylab.org> wrote:
>... so this patch adds protection to buf, moves buf into
>printk (as a static array), AND allows _SAFE_ recursion by kmalloc'ing a
>new buffer if "buf" is in use.
kmalloc(,GFP_KERNEL) in printk is not safe. Lots of code that calls
printk is not allowed to sleep which means that printk is never allowed
to sleep - kmalloc(,GFP_KERNEL) can sleep. Also kmalloc can call back
to printk, unlikely but a possible source of a runaway loop which will
blow the kernel stack.
Instead of allocating another buffer, just count how many times you
failed because the lock was in use. The code that owns the buffer can
issue the original message then check if the lost message counter has
changed and issue a message "BUG: <n> printk messages lost". Far safer
than calling other kernel services.
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