| Message ID | CAH5vBdLJqoB7x_r-8USiduK1tYPrfrXzqhtzGmg8U9VdQHEnEg@mail.gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Jul 10, 2012 at 12:00 AM, cheng renquan <crquan@gmail.com> wrote: > $ git diff HEAD -- drivers/acpi/scan.c > diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c > index 85cbfdc..7d26ae0 100644 > --- a/drivers/acpi/scan.c > +++ b/drivers/acpi/scan.c > @@ -28,7 +28,7 @@ extern struct acpi_device *acpi_root; > > static const char *dummy_hid = "device"; > > -static LIST_HEAD(acpi_device_list); > static LIST_HEAD(acpi_bus_id_list); > DEFINE_MUTEX(acpi_device_lock); > LIST_HEAD(acpi_wakeup_device_list); fortunately a later step of gcc optimization deleted that variable so it doesn't consume space in the final vmlinux, only the really in-use variable like the next acpi_bus_id_list consumed space; $ eu-readelf -s drivers/acpi/scan.o |egrep '(acpi_device_list|acpi_bus_id_list)' 35: 00000000000000b0 16 OBJECT LOCAL DEFAULT 3 acpi_bus_id_list $ eu-readelf -s vmlinux |egrep '(acpi_device_list|acpi_bus_id_list)' 24029: ffffffff81a62bc0 16 OBJECT LOCAL DEFAULT 15 acpi_bus_id_list anyway, we'd better to delete the acpi_device_list from the source; -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
=== $ git diff HEAD -- drivers/acpi/scan.c diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c index 85cbfdc..7d26ae0 100644 --- a/drivers/acpi/scan.c +++ b/drivers/acpi/scan.c @@ -28,7 +28,7 @@ extern struct acpi_device *acpi_root; static const char *dummy_hid = "device"; -static LIST_HEAD(acpi_device_list); static LIST_HEAD(acpi_bus_id_list); DEFINE_MUTEX(acpi_device_lock); LIST_HEAD(acpi_wakeup_device_list);
I just came across this file and found this LIST_HEAD(acpi_device_list) was referred in early days before 2.6.11 but not in use nowadays, ^1da177e drivers/acpi/scan.c (Linus Torvalds 2005-04-16 15:20:36 -0700 31) static LIST_HEAD(acpi_device_list); it is expanded to this line of referring itself form so gcc won't emit a warning, static struct list_head acpi_device_list = { &(acpi_device_list), &(acpi_device_list) }; If change to this line of just declaration then it could really cause a gcc warning: +static struct list_head acpi_device_list; drivers/acpi/scan.c:31:25: warning: ‘acpi_device_list’ defined but not used [-Wunused-variable] Now I'm guessing the kernel code may have more such dead variables, at least we could do a globally search to see there are more LIST_HEAD declaration without a 2nd reference; but does anyone have done this before or know any existing tools / such static analysis approaches? Thanks,