Messages in this thread | | | Date | Mon, 19 Jan 2015 20:19:25 +0100 | From | Oleg Nesterov <> | Subject | Re: [RFC/PATCH] init/main.c: Simplify initcall_blacklisted() |
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On 01/17, Rasmus Villemoes wrote: > > Using kasprintf to get the function name makes us look up the name > twice, along with all the vsnprintf overhead of parsing the format > string etc. It also means there is an allocation failure case to deal > with. Since symbol_string in vsprintf.c would anyway allocate an array > of size KSYM_SYMBOL_LEN on the stack, that might as well be done up > here. > > Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> > --- > > Notes: > I don't know how expensive it is to do the symbol lookup for each > initcall. It might be worthwhile adding an > > if (list_empty(&blacklisted_initcalls)) > return false; > > at the very beginning of initcall_blacklisted(), since this is a debug > feature and the blacklist is indeed usually empty.
If we want to optimize this... I am wondering if we can change initcall_blacklist()
- entry->buf = alloc_bootmem(strlen(str_entry) + 1); + ebtry->fn = kallsyms_lookup_name(str_entry);
and then change initcall_blacklisted() to just compare the pointers.
Oleg.
> init/main.c | 8 ++------ > 1 file changed, 2 insertions(+), 6 deletions(-) > > diff --git a/init/main.c b/init/main.c > index 61b993767db5..286602b677de 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -733,22 +733,18 @@ static bool __init_or_module initcall_blacklisted(initcall_t fn) > { > struct list_head *tmp; > struct blacklist_entry *entry; > - char *fn_name; > + char fn_name[KSYM_SYMBOL_LEN]; > > - fn_name = kasprintf(GFP_KERNEL, "%pf", fn); > - if (!fn_name) > - return false; > + sprint_symbol_no_offset(fn_name, (unsigned long)fn); > > list_for_each(tmp, &blacklisted_initcalls) { > entry = list_entry(tmp, struct blacklist_entry, next); > if (!strcmp(fn_name, entry->buf)) { > pr_debug("initcall %s blacklisted\n", fn_name); > - kfree(fn_name); > return true; > } > } > > - kfree(fn_name); > return false; > } > #else > -- > 2.1.3 >
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