Messages in this thread | | | Date | Fri, 7 Nov 2008 09:32:49 +0100 | From | Ingo Molnar <> | Subject | Re: [patch] add /proc/pid/stack to dump task's stack trace |
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* Alexey Dobriyan <adobriyan@gmail.com> wrote:
> On Fri, Nov 07, 2008 at 08:59:25AM +0100, Ingo Molnar wrote: > > > > * Ingo Molnar <mingo@elte.hu> wrote: > > > > > > > + * buffer size used for proc read. See proc_info_read(). > > > > > + * 4K page size but our output routines use some slack for overruns > > > > > + */ > > > > > +#define PROC_BLOCK_SIZE (3*1024) > > > > > > That sounds like a proper limit - the hard limit for this particular > > > printout function is 4096-170, so we are well within the > > > PROC_BLOCK_SIZE range. > > > > ok, i've added Ken's patch to tip/core/stacktrace and started testing > > it. > > > > Alexey, i've added your Acked-by because you appeared to like the > > patch - let me know if i should remove it. > > Of course, I don't like it! > > Switch to seqfiles, add entry in TID table as well. > > The idea is good, though.
oh well - Ken, could you please switch it to seqfiles?
It should be something like this to convert the currently sweet and trivial function into a much more complex seqfile iterator splitup:
- the ::start method does the kmalloc of a loop state structure like this:
{ struct stack_trace backtrace; unsigned long entries[MAX_STACK_TRACE_DEPTH];
int iterator; }
and saves the trace. (struct stack_trace trace can be on-stack, it's only needed for the save_stack_trace() - and we keep the entries after that.)
- the ::stop method does the kfree of the loop state.
- the ::show method prints a single line, based on ->entries[->iterator]
- the ::next method does ->iterator++, and returns NULL if iterator reaches ->backtrace.nr_entries.
it will be more source code, larger kernel image, it will be more fragile and will be harder to review, and it wont actually matter in practice because 99.9999% of the backtraces we care about have a size smaller than 3K. (and where they get larger clipping them to the first 3K is perfectly fine)
Ingo
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