Messages in this thread |  | | Subject | Re: [PATCH] printk: Add best-effort printk() buffering. | From | Joe Perches <> | Date | Sun, 30 Apr 2017 09:11:56 -0700 |
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On Sun, 2017-04-30 at 22:54 +0900, Tetsuo Handa wrote: > Sometimes we want to printk() multiple lines in a group without being > disturbed by concurrent printk() from interrupts and/or other threads. > For example, mixed printk() output of multiple thread's dump makes it > hard to interpret. > > This patch introduces fixed-sized statically allocated buffers for > buffering printk() output for each thread/context in best effort > (i.e. up to PAGE_SIZE bytes, up to 16 concurrent printk() users). [] > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c [] > +#define MAX_PRINTK_BUFFERS 16 > +static struct printk_buffer { > + unsigned long context; /* printk_context() */ > + unsigned int nested; > + unsigned int used; /* Valid bytes in buf[]. */ > + char buf[PAGE_SIZE]; > +} printk_buffers[MAX_PRINTK_BUFFERS];
Perhaps these buffers could be acquired by alloc_page rather than be static structures and the sizeof buf[PAGE_SIZE] should be reduced by sizeof(unsigned long) + sizeof(unsigned int) + sizeof(unsigned int) so that struct printk_buffers is exactly PAGE_SIZE.
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