Messages in this thread | | | Date | Thu, 24 Sep 2020 10:45:55 +0200 | From | Petr Mladek <> | Subject | Re: [PATCH printk 3/5] printk: use buffer pool for sprint buffers |
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On Thu 2020-09-24 14:40:58, Sergey Senozhatsky wrote: > On (20/09/23 17:11), Petr Mladek wrote: > > > > AFAIK, there is one catch. We need to use va_copy() around > > the 1st call because va_format can be proceed only once. > > > > Current printk() should be good enough for reporting, say, "Kernel > stack overflow" errors. Is extra pressure that va_copy() adds something > that we need to consider?
The thing is that vsprintf() traverses the arguments using va_arg(). It modifies internal values so that the next va_arg() will read the next value.
If we want to call vsprintf() twice then we need to reset the internal va_list states. My understanding is that va_copy() is the only legal way when we are already nested inside va_start()/va_end().
See also the commit 5756b76e4db643d8f7 ("vsprintf: make %pV handling compatible with kasprintf()").
Best Regards, Petr
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