On Monday, November 03, 2014 01:16:37 PM Lv Zheng wrote:
> There is wait code in the QR_SC command processing, which makes it not
> suitable to be put into a work queue item (see bug 82611). And there is
> case that the SCI_EVT cannot trigger GPE, though all commands have polling
> mode implemented, the event cannot be polled (see bug 77431).
>
> So if the QR_SC command can be put into a seperate IRQ thread, then the
> work queue will not be blocked by the QR_SC command processing and we can
> also trigger polling using the thread. Using IRQ thread also allows us to
> change the EC GPE handler into the threaded IRQ model when possible.
>
> This patch thus adds the IRQ polling thread for SCI_EVT polling and removes
> QR_SC processing work item.
>
> The reasons why we do not put a loop in the event poller to poll event
> until the returned query value is 0:
> Some platforms return non 0 query value even when SCI_EVT=0, if we put a
> loop in the poller, our command flush mechanism could never execute to
> an end thus the system suspending process could be blocked. One SCI_EVT
> triggering one QR_EC is current logic and has been proven to be working
> for so long time.
>
> The reasons why it is not implemented directly using threaded IRQ are:
> 1. ACPICA doesn't support threaded IRQ as not all of the OSPMs support
> threaded IRQ while GPE handler registerations are done through ACPICA.
> 2. The IRQ processing code need to be identical for both the IRQ handler
> and the thread callback, while currently, though the command GPE
> handling is ready for both IRQ and polling mode, only the event GPE is
> is polled in the event polling thread and the command is polled in the
> user threads.
> So we use a standalone kernel thread, if the above situations are changed
> in the future, we can easily convert the code into the threaded IRQ style.
>
> The old EC_FLAGS_QUERY_PENDING is converted to EC_FLAGS_EVENT_ENABLED in
> this patch, so that its naming is consistent with EC_FLAGS_EVENT_PENDING.
> The original flag doesn't co-work with SCI_EVT well, this patch refines
> its usage by enforcing a event polling wakeup indication as:
> EC_FLAGS_EVENT_ENABLED && EC_FLAGS_EVENT_PENDING
> So unless the both of the flags are set, the threaded event poller will
> not be woken up.
>
> This patch invokes acpi_ec_submit_request() after having detected SCI_EVT
> and invokes acpi_ec_complete_request() before having the QR_EC command
> processed. This is useful for implementing GPE storm prevention for
> malicous "level triggered" SCI_EVT. But the storm prevention is not
> implemented in this patch.
>
> Since the acpi_ec_submit_request() invoked after detecting the SCI_EVT is
> paired with acpi_ec_complete_request() invoked after completing QR_EC
> command, acpi_ec_submit_flushable_request() then need to be modified to
> allow QR_EC command to be submitted during this period to revert the
> increased reference count. This period can be determined by the event
> polling indication:
> EC_FLAGS_EVENT_ENABLED && EC_FLAGS_EVENT_PENDING
> Without enhancing this check in acpi_ec_submit_flushable_request(), QR_EC
> command will not be executed to decrease the reference count added after
> detecting the SCI_EVT, thus the system suspending will be blocked because
> the reference count equals to 2. Such check is common for flushing code.
>
> Reference: https://bugzilla.kernel.org/show_bug.cgi?id=82611
> Reference: https://bugzilla.kernel.org/show_bug.cgi?id=77431
> Signed-off-by: Lv Zheng <[email protected]>
> Tested-by: Ortwin Glück <[email protected]>
> ---
> drivers/acpi/ec.c | 194
> ++++++++++++++++++++++++++++++++++-------------
> drivers/acpi/internal.h | 1 +
> 2 files changed, 144 insertions(+), 51 deletions(-)
>
> diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
> index a76794a..7089081 100644
> --- a/drivers/acpi/ec.c
> +++ b/drivers/acpi/ec.c
> @@ -44,6 +44,7 @@
> #include <linux/slab.h>
> #include <linux/acpi.h>
> #include <linux/dmi.h>
> +#include <linux/kthread.h>
> #include <asm/io.h>
>
> #include "internal.h"
> @@ -75,7 +76,8 @@ enum ec_command {
> * when trying to clear the EC */
>
> enum {
> - EC_FLAGS_QUERY_PENDING, /* Query is pending */
> + EC_FLAGS_EVENT_ENABLED, /* Event is enabled */
> + EC_FLAGS_EVENT_PENDING, /* Event is pending */
> EC_FLAGS_GPE_STORM, /* GPE storm detected */
> EC_FLAGS_HANDLERS_INSTALLED, /* Handlers for GPE and
> * OpReg are installed */
> @@ -124,6 +126,7 @@ struct transaction {
> static struct acpi_ec_query_handler *
> acpi_ec_get_query_handler(struct acpi_ec_query_handler *handler);
> static void acpi_ec_put_query_handler(struct acpi_ec_query_handler *handler);
> +static int acpi_ec_sync_query(struct acpi_ec *ec, u8 *data);
>
> struct acpi_ec *boot_ec, *first_ec;
> EXPORT_SYMBOL(first_ec);
> @@ -149,6 +152,12 @@ static bool acpi_ec_flushed(struct acpi_ec *ec)
> return ec->reference_count == 1;
> }
>
> +static bool acpi_ec_has_pending_event(struct acpi_ec *ec)
> +{
> + return test_bit(EC_FLAGS_EVENT_ENABLED, &ec->flags) &&
> + test_bit(EC_FLAGS_EVENT_PENDING, &ec->flags);
> +}
> +
> /* --------------------------------------------------------------------------
> * GPE Enhancement
> *
> -------------------------------------------------------------------------- */
> @@ -177,20 +186,93 @@ static void acpi_ec_complete_request(struct acpi_ec *ec)
> * the flush operation is not in
> * progress
> * @ec: the EC device
> + * @check_event: check whether event is pending
> *
> * This function must be used before taking a new action that should hold
> * the reference count. If this function returns false, then the action
> * must be discarded or it will prevent the flush operation from being
> * completed.
> + *
> + * During flushing, QR_EC command need to pass this check when there is a
> + * pending event, so that the reference count held for the pending event
> + * can be decreased by the completion of the QR_EC command.
> */
> -static bool acpi_ec_submit_flushable_request(struct acpi_ec *ec)
> +static bool acpi_ec_submit_flushable_request(struct acpi_ec *ec,
> + bool check_event)
> {
> - if (!acpi_ec_started(ec))
> - return false;
> + if (!acpi_ec_started(ec)) {
> + if (!check_event || !acpi_ec_has_pending_event(ec))
> + return false;
> + }
> acpi_ec_submit_request(ec);
> return true;
> }
>
> +static void acpi_ec_enable_event(struct acpi_ec *ec)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&ec->lock, flags);
> + /* Hold reference for pending event */
> + if (!acpi_ec_submit_flushable_request(ec, false)) {
> + spin_unlock_irqrestore(&ec->lock, flags);
> + return;
> + }
> + set_bit(EC_FLAGS_EVENT_ENABLED, &ec->flags);
> + if (test_bit(EC_FLAGS_EVENT_PENDING, &ec->flags)) {
> + pr_debug("***** Event pending *****\n");
> + wake_up_process(ec->thread);
> + spin_unlock_irqrestore(&ec->lock, flags);
> + return;
> + }
> + acpi_ec_complete_request(ec);
> + spin_unlock_irqrestore(&ec->lock, flags);
> +}
> +
> +static void __acpi_ec_set_event(struct acpi_ec *ec)
> +{
> + /* Hold reference for pending event */
> + if (!acpi_ec_submit_flushable_request(ec, false))
> + return;
> + if (!test_and_set_bit(EC_FLAGS_EVENT_PENDING, &ec->flags)) {
> + pr_debug("***** Event pending *****\n");
> + if (test_bit(EC_FLAGS_EVENT_ENABLED, &ec->flags)) {
> + wake_up_process(ec->thread);
> + return;
> + }
> + }
> + acpi_ec_complete_request(ec);
> +}
> +
> +static void __acpi_ec_complete_event(struct acpi_ec *ec)
> +{
> + if (test_and_clear_bit(EC_FLAGS_EVENT_PENDING, &ec->flags)) {
> + /* Unhold reference for pending event */
> + acpi_ec_complete_request(ec);
> + pr_debug("***** Event running *****\n");
> + }
> +}
> +
> +int acpi_ec_wait_for_event(struct acpi_ec *ec)
> +{
> + unsigned long flags;
> +
> + set_current_state(TASK_INTERRUPTIBLE);
> + while (!kthread_should_stop()) {
> + spin_lock_irqsave(&ec->lock, flags);
> + if (acpi_ec_has_pending_event(ec)) {
> + spin_unlock_irqrestore(&ec->lock, flags);
> + __set_current_state(TASK_RUNNING);
> + return 0;
> + }
> + spin_unlock_irqrestore(&ec->lock, flags);
> + schedule();
> + set_current_state(TASK_INTERRUPTIBLE);
> + }
> + __set_current_state(TASK_RUNNING);
> + return -1;
> +}
> +
> /* --------------------------------------------------------------------------
> * Transaction Management
> *
> -------------------------------------------------------------------------- */
> @@ -298,7 +380,7 @@ static bool advance_transaction(struct acpi_ec *ec)
> t->flags |= ACPI_EC_COMMAND_COMPLETE;
> wakeup = true;
> }
> - return wakeup;
> + goto out;
> } else {
> if (EC_FLAGS_QUERY_HANDSHAKE &&
> !(status & ACPI_EC_FLAG_SCI) &&
> @@ -312,9 +394,11 @@ static bool advance_transaction(struct acpi_ec *ec)
> } else if ((status & ACPI_EC_FLAG_IBF) == 0) {
> acpi_ec_write_cmd(ec, t->command);
> t->flags |= ACPI_EC_COMMAND_POLL;
> + if (t->command == ACPI_EC_COMMAND_QUERY)
> + __acpi_ec_complete_event(ec);
> } else
> goto err;
> - return wakeup;
> + goto out;
> }
> err:
> /*
> @@ -325,6 +409,10 @@ err:
> if (in_interrupt() && t)
> ++t->irq_count;
> }
> +out:
> + if (status & ACPI_EC_FLAG_SCI &&
> + (!t || t->flags & ACPI_EC_COMMAND_COMPLETE))
> + __acpi_ec_set_event(ec);
> return wakeup;
> }
>
> @@ -335,17 +423,6 @@ static void start_transaction(struct acpi_ec *ec)
> (void)advance_transaction(ec);
> }
>
> -static int acpi_ec_sync_query(struct acpi_ec *ec, u8 *data);
> -
> -static int ec_check_sci_sync(struct acpi_ec *ec, u8 state)
> -{
> - if (state & ACPI_EC_FLAG_SCI) {
> - if (!test_and_set_bit(EC_FLAGS_QUERY_PENDING, &ec->flags))
> - return acpi_ec_sync_query(ec, NULL);
> - }
> - return 0;
> -}
> -
> static int ec_poll(struct acpi_ec *ec)
> {
> unsigned long flags;
> @@ -384,12 +461,13 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec
> *ec,
> unsigned long tmp;
> int ret = 0;
>
> + bool is_query = !!(t->command == ACPI_EC_COMMAND_QUERY);
> if (EC_FLAGS_MSI)
> udelay(ACPI_EC_MSI_UDELAY);
> /* start transaction */
> spin_lock_irqsave(&ec->lock, tmp);
> /* Enable GPE for command processing (IBF=0/OBF=1) */
> - if (!acpi_ec_submit_flushable_request(ec)) {
> + if (!acpi_ec_submit_flushable_request(ec, is_query)) {
> ret = -EINVAL;
> goto unlock;
> }
> @@ -398,10 +476,6 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec
> *ec,
> pr_debug("***** Command(%s) started *****\n",
> acpi_ec_cmd_string(t->command));
> start_transaction(ec);
> - if (ec->curr->command == ACPI_EC_COMMAND_QUERY) {
> - clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags);
> - pr_debug("***** Event stopped *****\n");
> - }
> spin_unlock_irqrestore(&ec->lock, tmp);
> ret = ec_poll(ec);
> spin_lock_irqsave(&ec->lock, tmp);
> @@ -440,8 +514,6 @@ static int acpi_ec_transaction(struct acpi_ec *ec, struct
> transaction *t)
>
> status = acpi_ec_transaction_unlocked(ec, t);
>
> - /* check if we received SCI during transaction */
> - ec_check_sci_sync(ec, acpi_ec_read_status(ec));
> if (test_bit(EC_FLAGS_GPE_STORM, &ec->flags)) {
> msleep(1);
> /* It is safe to enable the GPE outside of the transaction. */
> @@ -792,29 +864,6 @@ static int acpi_ec_sync_query(struct acpi_ec *ec, u8
> *data)
> return 0;
> }
>
> -static void acpi_ec_gpe_query(void *ec_cxt)
> -{
> - struct acpi_ec *ec = ec_cxt;
> -
> - if (!ec)
> - return;
> - mutex_lock(&ec->mutex);
> - acpi_ec_sync_query(ec, NULL);
> - mutex_unlock(&ec->mutex);
> -}
> -
> -static int ec_check_sci(struct acpi_ec *ec, u8 state)
> -{
> - if (state & ACPI_EC_FLAG_SCI) {
> - if (!test_and_set_bit(EC_FLAGS_QUERY_PENDING, &ec->flags)) {
> - pr_debug("***** Event started *****\n");
> - return acpi_os_execute(OSL_NOTIFY_HANDLER,
> - acpi_ec_gpe_query, ec);
> - }
> - }
> - return 0;
> -}
> -
> static u32 acpi_ec_gpe_handler(acpi_handle gpe_device,
> u32 gpe_number, void *data)
> {
> @@ -825,10 +874,46 @@ static u32 acpi_ec_gpe_handler(acpi_handle gpe_device,
> if (advance_transaction(ec))
> wake_up(&ec->wait);
> spin_unlock_irqrestore(&ec->lock, flags);
> - ec_check_sci(ec, acpi_ec_read_status(ec));
> return ACPI_INTERRUPT_HANDLED | ACPI_REENABLE_GPE;
> }
>
> +static int acpi_ec_event_poller(void *context)
> +{
> + struct acpi_ec *ec = context;
> +
> + while (!acpi_ec_wait_for_event(ec)) {
> + pr_debug("***** Event poller started *****\n");
> + mutex_lock(&ec->mutex);
> + (void)acpi_ec_sync_query(ec, NULL);
> + mutex_unlock(&ec->mutex);
> + pr_debug("***** Event poller stopped *****\n");
> + }
> + return 0;
> +}
> +
> +static int ec_create_event_poller(struct acpi_ec *ec)
> +{
> + struct task_struct *t;
> +
> + t = kthread_run(acpi_ec_event_poller, ec, "ec/gpe-%lu", ec->gpe);
Does it have to be a kernel thread?
What about using a workqueue instead?
> + if (IS_ERR(t)) {
> + pr_err("failed to create event poller %lu\n", ec->gpe);
> + return PTR_ERR(t);
> + }
> + get_task_struct(t);
> + ec->thread = t;
> + return 0;
> +}
> +
> +static void ec_delete_event_poller(struct acpi_ec *ec)
> +{
> + struct task_struct *t = ec->thread;
> +
> + ec->thread = NULL;
> + kthread_stop(t);
> + put_task_struct(t);
> +}
> +
> /* --------------------------------------------------------------------------
> * Address Space Management
> *
> -------------------------------------------------------------------------- */
> @@ -884,7 +969,6 @@ static struct acpi_ec *make_acpi_ec(void)
>
> if (!ec)
> return NULL;
> - ec->flags = 1 << EC_FLAGS_QUERY_PENDING;
> mutex_init(&ec->mutex);
> init_waitqueue_head(&ec->wait);
> INIT_LIST_HEAD(&ec->list);
> @@ -940,15 +1024,21 @@ ec_parse_device(acpi_handle handle, u32 Level, void
> *context, void **retval)
>
> static int ec_install_handlers(struct acpi_ec *ec)
> {
> + int ret;
> acpi_status status;
>
> if (test_bit(EC_FLAGS_HANDLERS_INSTALLED, &ec->flags))
> return 0;
> + ret = ec_create_event_poller(ec);
> + if (ret)
> + return ret;
> status = acpi_install_gpe_handler(NULL, ec->gpe,
> ACPI_GPE_EDGE_TRIGGERED,
> &acpi_ec_gpe_handler, ec);
> - if (ACPI_FAILURE(status))
> + if (ACPI_FAILURE(status)) {
> + ec_delete_event_poller(ec);
> return -ENODEV;
> + }
>
> acpi_ec_start(ec);
> status = acpi_install_address_space_handler(ec->handle,
> @@ -968,6 +1058,7 @@ static int ec_install_handlers(struct acpi_ec *ec)
> acpi_ec_stop(ec);
> acpi_remove_gpe_handler(NULL, ec->gpe,
> &acpi_ec_gpe_handler);
> + ec_delete_event_poller(ec);
> return -ENODEV;
> }
> }
> @@ -985,6 +1076,7 @@ static void ec_remove_handlers(struct acpi_ec *ec)
> if (ACPI_FAILURE(acpi_remove_gpe_handler(NULL, ec->gpe,
> &acpi_ec_gpe_handler)))
> pr_err("failed to remove gpe handler\n");
> + ec_delete_event_poller(ec);
> clear_bit(EC_FLAGS_HANDLERS_INSTALLED, &ec->flags);
> }
>
> @@ -1032,7 +1124,7 @@ static int acpi_ec_add(struct acpi_device *device)
> ret = ec_install_handlers(ec);
>
> /* EC is fully operational, allow queries */
> - clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags);
> + acpi_ec_enable_event(ec);
>
> /* Clear stale _Q events if hardware might require that */
> if (EC_FLAGS_CLEAR_ON_RESUME) {
> diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
> index bbcfe0b..20a569c 100644
> --- a/drivers/acpi/internal.h
> +++ b/drivers/acpi/internal.h
> @@ -128,6 +128,7 @@ struct acpi_ec {
> struct list_head list;
> struct transaction *curr;
> spinlock_t lock;
> + struct task_struct *thread;
> };
>
> extern struct acpi_ec *first_ec;
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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