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debug: Add _ONCE() logic to report_bug()

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Josh suggested moving the _ONCE logic inside the trap handler, using a
bit in the bug_entry::flags field, avoiding the need for the extra
variable.

Sadly this only works for WARN_ON_ONCE(), since the others have
printk() statements prior to triggering the trap.

Still, this saves a fair amount of text and some data:

  text         data       filename
  10682460     4530992    defconfig-build/vmlinux.orig
  10665111     4530096    defconfig-build/vmlinux.patched

Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2017-02-25 08:56:53 +01:00 • committed by Ingo Molnar
parent 70579a86e3
commit 19d436268d
10 changed files with 52 additions and 25 deletions
Download patch file Download diff file Expand all files Collapse all files

28
lib/bug.c
View file

@ -47,7 +47,7 @@
#include <linux/sched.h>
#include <linux/rculist.h>
extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
extern struct bug_entry __start___bug_table[], __stop___bug_table[];
static inline unsigned long bug_addr(const struct bug_entry *bug)
{
@ -62,10 +62,10 @@ static inline unsigned long bug_addr(const struct bug_entry *bug)
/* Updates are protected by module mutex */
static LIST_HEAD(module_bug_list);
static const struct bug_entry *module_find_bug(unsigned long bugaddr)
static struct bug_entry *module_find_bug(unsigned long bugaddr)
{
struct module *mod;
const struct bug_entry *bug = NULL;
struct bug_entry *bug = NULL;
rcu_read_lock_sched();
list_for_each_entry_rcu(mod, &module_bug_list, bug_list) {
@ -122,15 +122,15 @@ void module_bug_cleanup(struct module *mod)
#else
static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
static inline struct bug_entry *module_find_bug(unsigned long bugaddr)
{
return NULL;
}
#endif
const struct bug_entry *find_bug(unsigned long bugaddr)
struct bug_entry *find_bug(unsigned long bugaddr)
{
const struct bug_entry *bug;
struct bug_entry *bug;
for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
if (bugaddr == bug_addr(bug))
@ -141,9 +141,9 @@ const struct bug_entry *find_bug(unsigned long bugaddr)
enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
{
const struct bug_entry *bug;
struct bug_entry *bug;
const char *file;
unsigned line, warning;
unsigned line, warning, once, done;
if (!is_valid_bugaddr(bugaddr))
return BUG_TRAP_TYPE_NONE;
@ -164,6 +164,18 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
line = bug->line;
#endif
warning = (bug->flags & BUGFLAG_WARNING) != 0;
once = (bug->flags & BUGFLAG_ONCE) != 0;
done = (bug->flags & BUGFLAG_DONE) != 0;
if (warning && once) {
if (done)
return BUG_TRAP_TYPE_WARN;
/*
* Since this is the only store, concurrency is not an issue.
*/
bug->flags |= BUGFLAG_DONE;
}
}
if (warning) {