Re: e1000 horridness (was Re: [Bug #11342] Linux 2.6.27-rc3: kernel BUG at mm/vmalloc.c - bisected)

Kok, Auke
2008-08-26T20:14:18Z

Linus Torvalds wrote:
>
> On Tue, 26 Aug 2008, Jeff Garzik wrote:
>> e1000_check_options builds a struct (singular) on the stack, really... struct
>> e1000_option is reasonably small.
>
> No it doesn't.
>
> Look a bit more closely.
>
> It builds a struct (singular) MANY MANY times. It also then builds up a
> huge e1000_opt_list[] array, even though it is const and should be static
> (and const).
>
> I know. I wrote a patch to FIX it.

totally cool patch afaics - if I still maintained this driver I'd have this tested
and merged right away :)

I suppose Jeff Kirsher is already doing so right now.

I suppose that he'll have to look at the other Intel ethernet drivers as well :)

Jeff, please add my:

Reveiewed-by: Auke Kok <auke-jan.h.kok-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

Cheers,

Auke

>
> Here's the patch. It shrinks the stack from 1152 bytes to 192 bytes (the
> first version, that only did the e1000_option part, got it down to 600
> bytes). About half comes from not using multiple "e1000_option"
> structures, the other half comes from turning the "e1000_opt_list[]"
> arrays into "static const" instead, so that gcc doesn't copy them onto the
> stack.
>
> Most of the patch is actually doing things like turning
>
> struct struct e1000_option opt = {
>
> (which declares a _new_ e1000_option variable each time) into
>
> opt = (struct e1000_option) {
>
> which just re-uses the single variable.
>
> It becomes slightly larger than that, because some places the "opt = .."
> had to be moved around, since it's no longer a variable declaration, but a
> regular assignment.
>
> The rest is just adding "const" to the right places, and turning
>
> struct e1000_opt_list speed_list[] = ..
>
> into
>
> static const struct e1000_opt_list speed_list[] = ..
>
> instead, and fixing the indentation to be more straightforward.
>
> I have not tested the dang thing, but I think it's correct. And it turns
> stack usage from "totally horrible and broken" into "pretty reasonable".
>
> Linus
>
> ---
> drivers/net/e1000/e1000_param.c | 81 +++++++++++++++++++++-----------------
> 1 files changed, 45 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/net/e1000/e1000_param.c b/drivers/net/e1000/e1000_param.c
> index b9f90a5..213437d 100644
> --- a/drivers/net/e1000/e1000_param.c
> +++ b/drivers/net/e1000/e1000_param.c
> @@ -208,7 +208,7 @@ struct e1000_option {
> } r;
> struct { /* list_option info */
> int nr;
> - struct e1000_opt_list { int i; char *str; } *p;
> + const struct e1000_opt_list { int i; char *str; } *p;
> } l;
> } arg;
> };
> @@ -242,7 +242,7 @@ static int __devinit e1000_validate_option(unsigned int *value,
> break;
> case list_option: {
> int i;
> - struct e1000_opt_list *ent;
> + const struct e1000_opt_list *ent;
>
> for (i = 0; i < opt->arg.l.nr; i++) {
> ent = &opt->arg.l.p[i];
> @@ -279,7 +279,9 @@ static void e1000_check_copper_options(struct e1000_adapter *adapter);
>
> void __devinit e1000_check_options(struct e1000_adapter *adapter)
> {
> + struct e1000_option opt;
> int bd = adapter->bd_number;
> +
> if (bd >= E1000_MAX_NIC) {
> DPRINTK(PROBE, NOTICE,
> "Warning: no configuration for board #%i\n", bd);
> @@ -287,19 +289,21 @@ void __devinit e1000_check_options(struct e1000_adapter *adapter)
> }
>
> { /* Transmit Descriptor Count */
> - struct e1000_option opt = {
> + struct e1000_tx_ring *tx_ring = adapter->tx_ring;
> + int i;
> + e1000_mac_type mac_type = adapter->hw.mac_type;
> +
> + opt = (struct e1000_option) {
> .type = range_option,
> .name = "Transmit Descriptors",
> .err = "using default of "
> __MODULE_STRING(E1000_DEFAULT_TXD),
> .def = E1000_DEFAULT_TXD,
> - .arg = { .r = { .min = E1000_MIN_TXD }}
> + .arg = { .r = {
> + .min = E1000_MIN_TXD,
> + .max = mac_type < e1000_82544 ? E1000_MAX_TXD : E1000_MAX_82544_TXD
> + }}
> };
> - struct e1000_tx_ring *tx_ring = adapter->tx_ring;
> - int i;
> - e1000_mac_type mac_type = adapter->hw.mac_type;
> - opt.arg.r.max = mac_type < e1000_82544 ?
> - E1000_MAX_TXD : E1000_MAX_82544_TXD;
>
> if (num_TxDescriptors > bd) {
> tx_ring->count = TxDescriptors[bd];
> @@ -313,19 +317,21 @@ void __devinit e1000_check_options(struct e1000_adapter *adapter)
> tx_ring[i].count = tx_ring->count;
> }
> { /* Receive Descriptor Count */
> - struct e1000_option opt = {
> + struct e1000_rx_ring *rx_ring = adapter->rx_ring;
> + int i;
> + e1000_mac_type mac_type = adapter->hw.mac_type;
> +
> + opt = (struct e1000_option) {
> .type = range_option,
> .name = "Receive Descriptors",
> .err = "using default of "
> __MODULE_STRING(E1000_DEFAULT_RXD),
> .def = E1000_DEFAULT_RXD,
> - .arg = { .r = { .min = E1000_MIN_RXD }}
> + .arg = { .r = {
> + .min = E1000_MIN_RXD,
> + .max = mac_type < e1000_82544 ? E1000_MAX_RXD : E1000_MAX_82544_RXD
> + }}
> };
> - struct e1000_rx_ring *rx_ring = adapter->rx_ring;
> - int i;
> - e1000_mac_type mac_type = adapter->hw.mac_type;
> - opt.arg.r.max = mac_type < e1000_82544 ? E1000_MAX_RXD :
> - E1000_MAX_82544_RXD;
>
> if (num_RxDescriptors > bd) {
> rx_ring->count = RxDescriptors[bd];
> @@ -339,7 +345,7 @@ void __devinit e1000_check_options(struct e1000_adapter *adapter)
> rx_ring[i].count = rx_ring->count;
> }
> { /* Checksum Offload Enable/Disable */
> - struct e1000_option opt = {
> + opt = (struct e1000_option) {
> .type = enable_option,
> .name = "Checksum Offload",
> .err = "defaulting to Enabled",
> @@ -363,7 +369,7 @@ void __devinit e1000_check_options(struct e1000_adapter *adapter)
> { E1000_FC_FULL, "Flow Control Enabled" },
> { E1000_FC_DEFAULT, "Flow Control Hardware Default" }};
>
> - struct e1000_option opt = {
> + opt = (struct e1000_option) {
> .type = list_option,
> .name = "Flow Control",
> .err = "reading default settings from EEPROM",
> @@ -381,7 +387,7 @@ void __devinit e1000_check_options(struct e1000_adapter *adapter)
> }
> }
> { /* Transmit Interrupt Delay */
> - struct e1000_option opt = {
> + opt = (struct e1000_option) {
> .type = range_option,
> .name = "Transmit Interrupt Delay",
> .err = "using default of " __MODULE_STRING(DEFAULT_TIDV),
> @@ -399,7 +405,7 @@ void __devinit e1000_check_options(struct e1000_adapter *adapter)
> }
> }
> { /* Transmit Absolute Interrupt Delay */
> - struct e1000_option opt = {
> + opt = (struct e1000_option) {
> .type = range_option,
> .name = "Transmit Absolute Interrupt Delay",
> .err = "using default of " __MODULE_STRING(DEFAULT_TADV),
> @@ -417,7 +423,7 @@ void __devinit e1000_check_options(struct e1000_adapter *adapter)
> }
> }
> { /* Receive Interrupt Delay */
> - struct e1000_option opt = {
> + opt = (struct e1000_option) {
> .type = range_option,
> .name = "Receive Interrupt Delay",
> .err = "using default of " __MODULE_STRING(DEFAULT_RDTR),
> @@ -435,7 +441,7 @@ void __devinit e1000_check_options(struct e1000_adapter *adapter)
> }
> }
> { /* Receive Absolute Interrupt Delay */
> - struct e1000_option opt = {
> + opt = (struct e1000_option) {
> .type = range_option,
> .name = "Receive Absolute Interrupt Delay",
> .err = "using default of " __MODULE_STRING(DEFAULT_RADV),
> @@ -453,7 +459,7 @@ void __devinit e1000_check_options(struct e1000_adapter *adapter)
> }
> }
> { /* Interrupt Throttling Rate */
> - struct e1000_option opt = {
> + opt = (struct e1000_option) {
> .type = range_option,
> .name = "Interrupt Throttling Rate (ints/sec)",
> .err = "using default of " __MODULE_STRING(DEFAULT_ITR),
> @@ -497,7 +503,7 @@ void __devinit e1000_check_options(struct e1000_adapter *adapter)
> }
> }
> { /* Smart Power Down */
> - struct e1000_option opt = {
> + opt = (struct e1000_option) {
> .type = enable_option,
> .name = "PHY Smart Power Down",
> .err = "defaulting to Disabled",
> @@ -513,7 +519,7 @@ void __devinit e1000_check_options(struct e1000_adapter *adapter)
> }
> }
> { /* Kumeran Lock Loss Workaround */
> - struct e1000_option opt = {
> + opt = (struct e1000_option) {
> .type = enable_option,
> .name = "Kumeran Lock Loss Workaround",
> .err = "defaulting to Enabled",
> @@ -578,16 +584,18 @@ static void __devinit e1000_check_fiber_options(struct e1000_adapter *adapter)
>
> static void __devinit e1000_check_copper_options(struct e1000_adapter *adapter)
> {
> + struct e1000_option opt;
> unsigned int speed, dplx, an;
> int bd = adapter->bd_number;
>
> { /* Speed */
> - struct e1000_opt_list speed_list[] = {{ 0, "" },
> - { SPEED_10, "" },
> - { SPEED_100, "" },
> - { SPEED_1000, "" }};
> + static const struct e1000_opt_list speed_list[] = {
> + { 0, "" },
> + { SPEED_10, "" },
> + { SPEED_100, "" },
> + { SPEED_1000, "" }};
>
> - struct e1000_option opt = {
> + opt = (struct e1000_option) {
> .type = list_option,
> .name = "Speed",
> .err = "parameter ignored",
> @@ -604,11 +612,12 @@ static void __devinit e1000_check_copper_options(struct e1000_adapter *adapter)
> }
> }
> { /* Duplex */
> - struct e1000_opt_list dplx_list[] = {{ 0, "" },
> - { HALF_DUPLEX, "" },
> - { FULL_DUPLEX, "" }};
> + static const struct e1000_opt_list dplx_list[] = {
> + { 0, "" },
> + { HALF_DUPLEX, "" },
> + { FULL_DUPLEX, "" }};
>
> - struct e1000_option opt = {
> + opt = (struct e1000_option) {
> .type = list_option,
> .name = "Duplex",
> .err = "parameter ignored",
> @@ -637,7 +646,7 @@ static void __devinit e1000_check_copper_options(struct e1000_adapter *adapter)
> "parameter ignored\n");
> adapter->hw.autoneg_advertised = AUTONEG_ADV_DEFAULT;
> } else { /* Autoneg */
> - struct e1000_opt_list an_list[] =
> + static const struct e1000_opt_list an_list[] =
> #define AA "AutoNeg advertising "
> {{ 0x01, AA "10/HD" },
> { 0x02, AA "10/FD" },
> @@ -671,7 +680,7 @@ static void __devinit e1000_check_copper_options(struct e1000_adapter *adapter)
> { 0x2e, AA "1000/FD, 100/FD, 100/HD, 10/FD" },
> { 0x2f, AA "1000/FD, 100/FD, 100/HD, 10/FD, 10/HD" }};
>
> - struct e1000_option opt = {
> + opt = (struct e1000_option) {
> .type = list_option,
> .name = "AutoNeg",
> .err = "parameter ignored",