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    SubjectRe: [patch] pm_qos update fixing mmotm 2010-05-11 -dies in pm_qos_update_request()
    Date
    On Saturday 15 May 2010, mgross wrote:
    > I apologize for the goofy email address.
    >
    > The following is a fix for the crash reported by Valdis.
    >
    > The problem was that the original pm_qos silently fails when a request
    > update is passed to a parameter that has not been added to the list
    > yet. It seems that the e1000e is doing this. This update restores this
    > behavior.
    >
    > I need to think about how to better handle such abuse, but for now this
    > restores the original behavior.

    Can you please post a signed-off incremental patch against

    git://git.kernel.org/pub/scm/linux/kernel/git/rafael/suspend-2.6.git for-llinus

    that contains your original PM QOS update?

    Thanks,
    Rafael


    > Signed-off-by: markgross <markgross@thegnar.org>
    > --mgross
    >
    >
    > From 66700dc26ab7582bc7351541ba2e6241cc4b4144 Mon Sep 17 00:00:00 2001
    > From: mgross <mgross@mgross-desktop.(none)>
    > Date: Fri, 14 May 2010 19:05:44 -0700
    > Subject: [PATCH] PM QOS update
    > This patch changes the string based list management to a handle base
    > implementation to help with the hot path use of pm-qos, it also renames
    > much of the API to use "request" as opposed to "requirement" that was
    > used in the initial implementation. I did this because request more
    > accurately represents what it actually does.
    >
    > Also, I added a string based ABI for users wanting to use a string
    > interface. So if the user writes 0xDDDDDDDD formatted hex it will be
    > accepted by the interface. (someone asked me for it and I don't think
    > it hurts anything.)
    >
    > This patch updates some documentation input I got from Randy.
    >
    > This version handles a use case where pm_qos update requests need to
    > silently not fail if the update is being sent to a handle that is null.
    > This is what happened in the initial version of pm-qos if you used a
    > string that wasn't in the list.
    >
    > Signed-off-by: markgross <mgross@linux.intel.com>
    > ---
    > Documentation/power/pm_qos_interface.txt | 48 ++++---
    > drivers/acpi/processor_idle.c | 2 +-
    > drivers/cpuidle/governors/ladder.c | 2 +-
    > drivers/cpuidle/governors/menu.c | 2 +-
    > drivers/net/e1000e/netdev.c | 22 ++--
    > drivers/net/igbvf/netdev.c | 6 +-
    > drivers/net/wireless/ipw2x00/ipw2100.c | 11 +-
    > include/linux/netdevice.h | 4 +
    > include/linux/pm_qos_params.h | 14 +-
    > include/sound/pcm.h | 3 +-
    > kernel/pm_qos_params.c | 217 +++++++++++++++---------------
    > net/mac80211/mlme.c | 2 +-
    > sound/core/pcm.c | 3 -
    > sound/core/pcm_native.c | 14 +-
    > 14 files changed, 179 insertions(+), 171 deletions(-)
    >
    > diff --git a/Documentation/power/pm_qos_interface.txt b/Documentation/power/pm_qos_interface.txt
    > index c40866e..bfed898 100644
    > --- a/Documentation/power/pm_qos_interface.txt
    > +++ b/Documentation/power/pm_qos_interface.txt
    > @@ -18,44 +18,46 @@ and pm_qos_params.h. This is done because having the available parameters
    > being runtime configurable or changeable from a driver was seen as too easy to
    > abuse.
    >
    > -For each parameter a list of performance requirements is maintained along with
    > +For each parameter a list of performance requests is maintained along with
    > an aggregated target value. The aggregated target value is updated with
    > -changes to the requirement list or elements of the list. Typically the
    > -aggregated target value is simply the max or min of the requirement values held
    > +changes to the request list or elements of the list. Typically the
    > +aggregated target value is simply the max or min of the request values held
    > in the parameter list elements.
    >
    > From kernel mode the use of this interface is simple:
    > -pm_qos_add_requirement(param_id, name, target_value):
    > -Will insert a named element in the list for that identified PM_QOS parameter
    > -with the target value. Upon change to this list the new target is recomputed
    > -and any registered notifiers are called only if the target value is now
    > -different.
    >
    > -pm_qos_update_requirement(param_id, name, new_target_value):
    > -Will search the list identified by the param_id for the named list element and
    > -then update its target value, calling the notification tree if the aggregated
    > -target is changed. with that name is already registered.
    > +handle = pm_qos_add_request(param_class, target_value):
    > +Will insert an element into the list for that identified PM_QOS class with the
    > +target value. Upon change to this list the new target is recomputed and any
    > +registered notifiers are called only if the target value is now different.
    > +Clients of pm_qos need to save the returned handle.
    >
    > -pm_qos_remove_requirement(param_id, name):
    > -Will search the identified list for the named element and remove it, after
    > -removal it will update the aggregate target and call the notification tree if
    > -the target was changed as a result of removing the named requirement.
    > +void pm_qos_update_request(handle, new_target_value):
    > +Will update the list element pointed to by the handle with the new target value
    > +and recompute the new aggregated target, calling the notification tree if the
    > +target is changed.
    > +
    > +void pm_qos_remove_request(handle):
    > +Will remove the element. After removal it will update the aggregate target and
    > +call the notification tree if the target was changed as a result of removing
    > +the request.
    >
    >
    > From user mode:
    > -Only processes can register a pm_qos requirement. To provide for automatic
    > -cleanup for process the interface requires the process to register its
    > -parameter requirements in the following way:
    > +Only processes can register a pm_qos request. To provide for automatic
    > +cleanup of a process, the interface requires the process to register its
    > +parameter requests in the following way:
    >
    > To register the default pm_qos target for the specific parameter, the process
    > must open one of /dev/[cpu_dma_latency, network_latency, network_throughput]
    >
    > As long as the device node is held open that process has a registered
    > -requirement on the parameter. The name of the requirement is "process_<PID>"
    > -derived from the current->pid from within the open system call.
    > +request on the parameter.
    >
    > -To change the requested target value the process needs to write a s32 value to
    > -the open device node. This translates to a pm_qos_update_requirement call.
    > +To change the requested target value the process needs to write an s32 value to
    > +the open device node. Alternatively the user mode program could write a hex
    > +string for the value using 10 char long format e.g. "0x12345678". This
    > +translates to a pm_qos_update_request call.
    >
    > To remove the user mode request for a target value simply close the device
    > node.
    > diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
    > index 5939e7f..c3817e1 100644
    > --- a/drivers/acpi/processor_idle.c
    > +++ b/drivers/acpi/processor_idle.c
    > @@ -698,7 +698,7 @@ static int acpi_processor_power_seq_show(struct seq_file *seq, void *offset)
    > "max_cstate: C%d\n"
    > "maximum allowed latency: %d usec\n",
    > pr->power.state ? pr->power.state - pr->power.states : 0,
    > - max_cstate, pm_qos_requirement(PM_QOS_CPU_DMA_LATENCY));
    > + max_cstate, pm_qos_request(PM_QOS_CPU_DMA_LATENCY));
    >
    > seq_puts(seq, "states:\n");
    >
    > diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c
    > index 1c1ceb4..12c9890 100644
    > --- a/drivers/cpuidle/governors/ladder.c
    > +++ b/drivers/cpuidle/governors/ladder.c
    > @@ -67,7 +67,7 @@ static int ladder_select_state(struct cpuidle_device *dev)
    > struct ladder_device *ldev = &__get_cpu_var(ladder_devices);
    > struct ladder_device_state *last_state;
    > int last_residency, last_idx = ldev->last_state_idx;
    > - int latency_req = pm_qos_requirement(PM_QOS_CPU_DMA_LATENCY);
    > + int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
    >
    > /* Special case when user has set very strict latency requirement */
    > if (unlikely(latency_req == 0)) {
    > diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
    > index f8e57c6..b81ad9c 100644
    > --- a/drivers/cpuidle/governors/menu.c
    > +++ b/drivers/cpuidle/governors/menu.c
    > @@ -182,7 +182,7 @@ static u64 div_round64(u64 dividend, u32 divisor)
    > static int menu_select(struct cpuidle_device *dev)
    > {
    > struct menu_device *data = &__get_cpu_var(menu_devices);
    > - int latency_req = pm_qos_requirement(PM_QOS_CPU_DMA_LATENCY);
    > + int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
    > int i;
    > int multiplier;
    >
    > diff --git a/drivers/net/e1000e/netdev.c b/drivers/net/e1000e/netdev.c
    > index dbf8178..d5d55c6 100644
    > --- a/drivers/net/e1000e/netdev.c
    > +++ b/drivers/net/e1000e/netdev.c
    > @@ -2524,12 +2524,12 @@ static void e1000_configure_rx(struct e1000_adapter *adapter)
    > * excessive C-state transition latencies result in
    > * dropped transactions.
    > */
    > - pm_qos_update_requirement(PM_QOS_CPU_DMA_LATENCY,
    > - adapter->netdev->name, 55);
    > + pm_qos_update_request(
    > + adapter->netdev->pm_qos_req, 55);
    > } else {
    > - pm_qos_update_requirement(PM_QOS_CPU_DMA_LATENCY,
    > - adapter->netdev->name,
    > - PM_QOS_DEFAULT_VALUE);
    > + pm_qos_update_request(
    > + adapter->netdev->pm_qos_req,
    > + PM_QOS_DEFAULT_VALUE);
    > }
    > }
    >
    > @@ -2824,8 +2824,8 @@ int e1000e_up(struct e1000_adapter *adapter)
    >
    > /* DMA latency requirement to workaround early-receive/jumbo issue */
    > if (adapter->flags & FLAG_HAS_ERT)
    > - pm_qos_add_requirement(PM_QOS_CPU_DMA_LATENCY,
    > - adapter->netdev->name,
    > + adapter->netdev->pm_qos_req =
    > + pm_qos_add_request(PM_QOS_CPU_DMA_LATENCY,
    > PM_QOS_DEFAULT_VALUE);
    >
    > /* hardware has been reset, we need to reload some things */
    > @@ -2887,9 +2887,11 @@ void e1000e_down(struct e1000_adapter *adapter)
    > e1000_clean_tx_ring(adapter);
    > e1000_clean_rx_ring(adapter);
    >
    > - if (adapter->flags & FLAG_HAS_ERT)
    > - pm_qos_remove_requirement(PM_QOS_CPU_DMA_LATENCY,
    > - adapter->netdev->name);
    > + if (adapter->flags & FLAG_HAS_ERT) {
    > + pm_qos_remove_request(
    > + adapter->netdev->pm_qos_req);
    > + adapter->netdev->pm_qos_req = NULL;
    > + }
    >
    > /*
    > * TODO: for power management, we could drop the link and
    > diff --git a/drivers/net/igbvf/netdev.c b/drivers/net/igbvf/netdev.c
    > index 1b1edad..f16e981 100644
    > --- a/drivers/net/igbvf/netdev.c
    > +++ b/drivers/net/igbvf/netdev.c
    > @@ -48,6 +48,7 @@
    > #define DRV_VERSION "1.0.0-k0"
    > char igbvf_driver_name[] = "igbvf";
    > const char igbvf_driver_version[] = DRV_VERSION;
    > +struct pm_qos_request_list *igbvf_driver_pm_qos_req;
    > static const char igbvf_driver_string[] =
    > "Intel(R) Virtual Function Network Driver";
    > static const char igbvf_copyright[] = "Copyright (c) 2009 Intel Corporation.";
    > @@ -2899,7 +2900,7 @@ static int __init igbvf_init_module(void)
    > printk(KERN_INFO "%s\n", igbvf_copyright);
    >
    > ret = pci_register_driver(&igbvf_driver);
    > - pm_qos_add_requirement(PM_QOS_CPU_DMA_LATENCY, igbvf_driver_name,
    > + igbvf_driver_pm_qos_req = pm_qos_add_request(PM_QOS_CPU_DMA_LATENCY,
    > PM_QOS_DEFAULT_VALUE);
    >
    > return ret;
    > @@ -2915,7 +2916,8 @@ module_init(igbvf_init_module);
    > static void __exit igbvf_exit_module(void)
    > {
    > pci_unregister_driver(&igbvf_driver);
    > - pm_qos_remove_requirement(PM_QOS_CPU_DMA_LATENCY, igbvf_driver_name);
    > + pm_qos_remove_request(igbvf_driver_pm_qos_req);
    > + igbvf_driver_pm_qos_req = NULL;
    > }
    > module_exit(igbvf_exit_module);
    >
    > diff --git a/drivers/net/wireless/ipw2x00/ipw2100.c b/drivers/net/wireless/ipw2x00/ipw2100.c
    > index 9b72c45..2b05fe5 100644
    > --- a/drivers/net/wireless/ipw2x00/ipw2100.c
    > +++ b/drivers/net/wireless/ipw2x00/ipw2100.c
    > @@ -174,6 +174,8 @@ that only one external action is invoked at a time.
    > #define DRV_DESCRIPTION "Intel(R) PRO/Wireless 2100 Network Driver"
    > #define DRV_COPYRIGHT "Copyright(c) 2003-2006 Intel Corporation"
    >
    > +struct pm_qos_request_list *ipw2100_pm_qos_req;
    > +
    > /* Debugging stuff */
    > #ifdef CONFIG_IPW2100_DEBUG
    > #define IPW2100_RX_DEBUG /* Reception debugging */
    > @@ -1739,7 +1741,7 @@ static int ipw2100_up(struct ipw2100_priv *priv, int deferred)
    > /* the ipw2100 hardware really doesn't want power management delays
    > * longer than 175usec
    > */
    > - pm_qos_update_requirement(PM_QOS_CPU_DMA_LATENCY, "ipw2100", 175);
    > + pm_qos_update_request(ipw2100_pm_qos_req, 175);
    >
    > /* If the interrupt is enabled, turn it off... */
    > spin_lock_irqsave(&priv->low_lock, flags);
    > @@ -1887,8 +1889,7 @@ static void ipw2100_down(struct ipw2100_priv *priv)
    > ipw2100_disable_interrupts(priv);
    > spin_unlock_irqrestore(&priv->low_lock, flags);
    >
    > - pm_qos_update_requirement(PM_QOS_CPU_DMA_LATENCY, "ipw2100",
    > - PM_QOS_DEFAULT_VALUE);
    > + pm_qos_update_request(ipw2100_pm_qos_req, PM_QOS_DEFAULT_VALUE);
    >
    > /* We have to signal any supplicant if we are disassociating */
    > if (associated)
    > @@ -6669,7 +6670,7 @@ static int __init ipw2100_init(void)
    > if (ret)
    > goto out;
    >
    > - pm_qos_add_requirement(PM_QOS_CPU_DMA_LATENCY, "ipw2100",
    > + ipw2100_pm_qos_req = pm_qos_add_request(PM_QOS_CPU_DMA_LATENCY,
    > PM_QOS_DEFAULT_VALUE);
    > #ifdef CONFIG_IPW2100_DEBUG
    > ipw2100_debug_level = debug;
    > @@ -6692,7 +6693,7 @@ static void __exit ipw2100_exit(void)
    > &driver_attr_debug_level);
    > #endif
    > pci_unregister_driver(&ipw2100_pci_driver);
    > - pm_qos_remove_requirement(PM_QOS_CPU_DMA_LATENCY, "ipw2100");
    > + pm_qos_remove_request(ipw2100_pm_qos_req);
    > }
    >
    > module_init(ipw2100_init);
    > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
    > index fa8b476..3857517 100644
    > --- a/include/linux/netdevice.h
    > +++ b/include/linux/netdevice.h
    > @@ -31,6 +31,7 @@
    > #include <linux/if_link.h>
    >
    > #ifdef __KERNEL__
    > +#include <linux/pm_qos_params.h>
    > #include <linux/timer.h>
    > #include <linux/delay.h>
    > #include <linux/mm.h>
    > @@ -711,6 +712,9 @@ struct net_device {
    > * the interface.
    > */
    > char name[IFNAMSIZ];
    > +
    > + struct pm_qos_request_list *pm_qos_req;
    > +
    > /* device name hash chain */
    > struct hlist_node name_hlist;
    > /* snmp alias */
    > diff --git a/include/linux/pm_qos_params.h b/include/linux/pm_qos_params.h
    > index d74f75e..8ba440e 100644
    > --- a/include/linux/pm_qos_params.h
    > +++ b/include/linux/pm_qos_params.h
    > @@ -14,12 +14,14 @@
    > #define PM_QOS_NUM_CLASSES 4
    > #define PM_QOS_DEFAULT_VALUE -1
    >
    > -int pm_qos_add_requirement(int qos, char *name, s32 value);
    > -int pm_qos_update_requirement(int qos, char *name, s32 new_value);
    > -void pm_qos_remove_requirement(int qos, char *name);
    > +struct pm_qos_request_list;
    >
    > -int pm_qos_requirement(int qos);
    > +struct pm_qos_request_list *pm_qos_add_request(int pm_qos_class, s32 value);
    > +void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
    > + s32 new_value);
    > +void pm_qos_remove_request(struct pm_qos_request_list *pm_qos_req);
    >
    > -int pm_qos_add_notifier(int qos, struct notifier_block *notifier);
    > -int pm_qos_remove_notifier(int qos, struct notifier_block *notifier);
    > +int pm_qos_request(int pm_qos_class);
    > +int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier);
    > +int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier);
    >
    > diff --git a/include/sound/pcm.h b/include/sound/pcm.h
    > index 8b611a5..dd76cde 100644
    > --- a/include/sound/pcm.h
    > +++ b/include/sound/pcm.h
    > @@ -29,6 +29,7 @@
    > #include <linux/poll.h>
    > #include <linux/mm.h>
    > #include <linux/bitops.h>
    > +#include <linux/pm_qos_params.h>
    >
    > #define snd_pcm_substream_chip(substream) ((substream)->private_data)
    > #define snd_pcm_chip(pcm) ((pcm)->private_data)
    > @@ -365,7 +366,7 @@ struct snd_pcm_substream {
    > int number;
    > char name[32]; /* substream name */
    > int stream; /* stream (direction) */
    > - char latency_id[20]; /* latency identifier */
    > + struct pm_qos_request_list *latency_pm_qos_req; /* pm_qos request */
    > size_t buffer_bytes_max; /* limit ring buffer size */
    > struct snd_dma_buffer dma_buffer;
    > unsigned int dma_buf_id;
    > diff --git a/kernel/pm_qos_params.c b/kernel/pm_qos_params.c
    > index 3db49b9..dfa1425 100644
    > --- a/kernel/pm_qos_params.c
    > +++ b/kernel/pm_qos_params.c
    > @@ -2,7 +2,7 @@
    > * This module exposes the interface to kernel space for specifying
    > * QoS dependencies. It provides infrastructure for registration of:
    > *
    > - * Dependents on a QoS value : register requirements
    > + * Dependents on a QoS value : register requests
    > * Watchers of QoS value : get notified when target QoS value changes
    > *
    > * This QoS design is best effort based. Dependents register their QoS needs.
    > @@ -14,19 +14,21 @@
    > * timeout: usec <-- currently not used.
    > * throughput: kbs (kilo byte / sec)
    > *
    > - * There are lists of pm_qos_objects each one wrapping requirements, notifiers
    > + * There are lists of pm_qos_objects each one wrapping requests, notifiers
    > *
    > - * User mode requirements on a QOS parameter register themselves to the
    > + * User mode requests on a QOS parameter register themselves to the
    > * subsystem by opening the device node /dev/... and writing there request to
    > * the node. As long as the process holds a file handle open to the node the
    > * client continues to be accounted for. Upon file release the usermode
    > - * requirement is removed and a new qos target is computed. This way when the
    > - * requirement that the application has is cleaned up when closes the file
    > + * request is removed and a new qos target is computed. This way when the
    > + * request that the application has is cleaned up when closes the file
    > * pointer or exits the pm_qos_object will get an opportunity to clean up.
    > *
    > * Mark Gross <mgross@linux.intel.com>
    > */
    >
    > +/*#define DEBUG*/
    > +
    > #include <linux/pm_qos_params.h>
    > #include <linux/sched.h>
    > #include <linux/spinlock.h>
    > @@ -42,25 +44,25 @@
    > #include <linux/uaccess.h>
    >
    > /*
    > - * locking rule: all changes to requirements or notifiers lists
    > + * locking rule: all changes to requests or notifiers lists
    > * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
    > * held, taken with _irqsave. One lock to rule them all
    > */
    > -struct requirement_list {
    > +struct pm_qos_request_list {
    > struct list_head list;
    > union {
    > s32 value;
    > s32 usec;
    > s32 kbps;
    > };
    > - char *name;
    > + int pm_qos_class;
    > };
    >
    > static s32 max_compare(s32 v1, s32 v2);
    > static s32 min_compare(s32 v1, s32 v2);
    >
    > struct pm_qos_object {
    > - struct requirement_list requirements;
    > + struct pm_qos_request_list requests;
    > struct blocking_notifier_head *notifiers;
    > struct miscdevice pm_qos_power_miscdev;
    > char *name;
    > @@ -72,7 +74,7 @@ struct pm_qos_object {
    > static struct pm_qos_object null_pm_qos;
    > static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
    > static struct pm_qos_object cpu_dma_pm_qos = {
    > - .requirements = {LIST_HEAD_INIT(cpu_dma_pm_qos.requirements.list)},
    > + .requests = {LIST_HEAD_INIT(cpu_dma_pm_qos.requests.list)},
    > .notifiers = &cpu_dma_lat_notifier,
    > .name = "cpu_dma_latency",
    > .default_value = 2000 * USEC_PER_SEC,
    > @@ -82,7 +84,7 @@ static struct pm_qos_object cpu_dma_pm_qos = {
    >
    > static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
    > static struct pm_qos_object network_lat_pm_qos = {
    > - .requirements = {LIST_HEAD_INIT(network_lat_pm_qos.requirements.list)},
    > + .requests = {LIST_HEAD_INIT(network_lat_pm_qos.requests.list)},
    > .notifiers = &network_lat_notifier,
    > .name = "network_latency",
    > .default_value = 2000 * USEC_PER_SEC,
    > @@ -93,8 +95,7 @@ static struct pm_qos_object network_lat_pm_qos = {
    >
    > static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
    > static struct pm_qos_object network_throughput_pm_qos = {
    > - .requirements =
    > - {LIST_HEAD_INIT(network_throughput_pm_qos.requirements.list)},
    > + .requests = {LIST_HEAD_INIT(network_throughput_pm_qos.requests.list)},
    > .notifiers = &network_throughput_notifier,
    > .name = "network_throughput",
    > .default_value = 0,
    > @@ -135,31 +136,34 @@ static s32 min_compare(s32 v1, s32 v2)
    > }
    >
    >
    > -static void update_target(int target)
    > +static void update_target(int pm_qos_class)
    > {
    > s32 extreme_value;
    > - struct requirement_list *node;
    > + struct pm_qos_request_list *node;
    > unsigned long flags;
    > int call_notifier = 0;
    >
    > spin_lock_irqsave(&pm_qos_lock, flags);
    > - extreme_value = pm_qos_array[target]->default_value;
    > + extreme_value = pm_qos_array[pm_qos_class]->default_value;
    > list_for_each_entry(node,
    > - &pm_qos_array[target]->requirements.list, list) {
    > - extreme_value = pm_qos_array[target]->comparitor(
    > + &pm_qos_array[pm_qos_class]->requests.list, list) {
    > + extreme_value = pm_qos_array[pm_qos_class]->comparitor(
    > extreme_value, node->value);
    > }
    > - if (atomic_read(&pm_qos_array[target]->target_value) != extreme_value) {
    > + if (atomic_read(&pm_qos_array[pm_qos_class]->target_value) !=
    > + extreme_value) {
    > call_notifier = 1;
    > - atomic_set(&pm_qos_array[target]->target_value, extreme_value);
    > - pr_debug(KERN_ERR "new target for qos %d is %d\n", target,
    > - atomic_read(&pm_qos_array[target]->target_value));
    > + atomic_set(&pm_qos_array[pm_qos_class]->target_value,
    > + extreme_value);
    > + pr_debug(KERN_ERR "new target for qos %d is %d\n", pm_qos_class,
    > + atomic_read(&pm_qos_array[pm_qos_class]->target_value));
    > }
    > spin_unlock_irqrestore(&pm_qos_lock, flags);
    >
    > if (call_notifier)
    > - blocking_notifier_call_chain(pm_qos_array[target]->notifiers,
    > - (unsigned long) extreme_value, NULL);
    > + blocking_notifier_call_chain(
    > + pm_qos_array[pm_qos_class]->notifiers,
    > + (unsigned long) extreme_value, NULL);
    > }
    >
    > static int register_pm_qos_misc(struct pm_qos_object *qos)
    > @@ -185,125 +189,113 @@ static int find_pm_qos_object_by_minor(int minor)
    > }
    >
    > /**
    > - * pm_qos_requirement - returns current system wide qos expectation
    > + * pm_qos_request - returns current system wide qos expectation
    > * @pm_qos_class: identification of which qos value is requested
    > *
    > * This function returns the current target value in an atomic manner.
    > */
    > -int pm_qos_requirement(int pm_qos_class)
    > +int pm_qos_request(int pm_qos_class)
    > {
    > return atomic_read(&pm_qos_array[pm_qos_class]->target_value);
    > }
    > -EXPORT_SYMBOL_GPL(pm_qos_requirement);
    > +EXPORT_SYMBOL_GPL(pm_qos_request);
    >
    > /**
    > - * pm_qos_add_requirement - inserts new qos request into the list
    > + * pm_qos_add_request - inserts new qos request into the list
    > * @pm_qos_class: identifies which list of qos request to us
    > - * @name: identifies the request
    > * @value: defines the qos request
    > *
    > * This function inserts a new entry in the pm_qos_class list of requested qos
    > * performance characteristics. It recomputes the aggregate QoS expectations
    > - * for the pm_qos_class of parameters.
    > + * for the pm_qos_class of parameters, and returns the pm_qos_request list
    > + * element as a handle for use in updating and removal. Call needs to save
    > + * this handle for later use.
    > */
    > -int pm_qos_add_requirement(int pm_qos_class, char *name, s32 value)
    > +struct pm_qos_request_list *pm_qos_add_request(int pm_qos_class, s32 value)
    > {
    > - struct requirement_list *dep;
    > + struct pm_qos_request_list *dep;
    > unsigned long flags;
    >
    > - dep = kzalloc(sizeof(struct requirement_list), GFP_KERNEL);
    > + dep = kzalloc(sizeof(struct pm_qos_request_list), GFP_KERNEL);
    > if (dep) {
    > if (value == PM_QOS_DEFAULT_VALUE)
    > dep->value = pm_qos_array[pm_qos_class]->default_value;
    > else
    > dep->value = value;
    > - dep->name = kstrdup(name, GFP_KERNEL);
    > - if (!dep->name)
    > - goto cleanup;
    > + dep->pm_qos_class = pm_qos_class;
    >
    > spin_lock_irqsave(&pm_qos_lock, flags);
    > list_add(&dep->list,
    > - &pm_qos_array[pm_qos_class]->requirements.list);
    > + &pm_qos_array[pm_qos_class]->requests.list);
    > spin_unlock_irqrestore(&pm_qos_lock, flags);
    > update_target(pm_qos_class);
    > -
    > - return 0;
    > }
    >
    > -cleanup:
    > - kfree(dep);
    > - return -ENOMEM;
    > + return dep;
    > }
    > -EXPORT_SYMBOL_GPL(pm_qos_add_requirement);
    > +EXPORT_SYMBOL_GPL(pm_qos_add_request);
    >
    > /**
    > - * pm_qos_update_requirement - modifies an existing qos request
    > - * @pm_qos_class: identifies which list of qos request to us
    > - * @name: identifies the request
    > + * pm_qos_update_request - modifies an existing qos request
    > + * @pm_qos_req : handle to list element holding a pm_qos request to use
    > * @value: defines the qos request
    > *
    > - * Updates an existing qos requirement for the pm_qos_class of parameters along
    > + * Updates an existing qos request for the pm_qos_class of parameters along
    > * with updating the target pm_qos_class value.
    > *
    > - * If the named request isn't in the list then no change is made.
    > + * Attempts are made to make this code callable on hot code paths.
    > */
    > -int pm_qos_update_requirement(int pm_qos_class, char *name, s32 new_value)
    > +void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
    > + s32 new_value)
    > {
    > unsigned long flags;
    > - struct requirement_list *node;
    > int pending_update = 0;
    > + s32 temp;
    >
    > - spin_lock_irqsave(&pm_qos_lock, flags);
    > - list_for_each_entry(node,
    > - &pm_qos_array[pm_qos_class]->requirements.list, list) {
    > - if (strcmp(node->name, name) == 0) {
    > - if (new_value == PM_QOS_DEFAULT_VALUE)
    > - node->value =
    > - pm_qos_array[pm_qos_class]->default_value;
    > - else
    > - node->value = new_value;
    > + if (pm_qos_req) { /*guard against callers passing in null */
    > + spin_lock_irqsave(&pm_qos_lock, flags);
    > + if (new_value == PM_QOS_DEFAULT_VALUE)
    > + temp = pm_qos_array[pm_qos_req->pm_qos_class]->
    > + default_value;
    > + else
    > + temp = new_value;
    > +
    > + if (temp != pm_qos_req->value) {
    > pending_update = 1;
    > - break;
    > + pm_qos_req->value = temp;
    > }
    > + spin_unlock_irqrestore(&pm_qos_lock, flags);
    > }
    > - spin_unlock_irqrestore(&pm_qos_lock, flags);
    > if (pending_update)
    > - update_target(pm_qos_class);
    > -
    > - return 0;
    > + update_target(pm_qos_req->pm_qos_class);
    > }
    > -EXPORT_SYMBOL_GPL(pm_qos_update_requirement);
    > +EXPORT_SYMBOL_GPL(pm_qos_update_request);
    >
    > /**
    > - * pm_qos_remove_requirement - modifies an existing qos request
    > - * @pm_qos_class: identifies which list of qos request to us
    > - * @name: identifies the request
    > + * pm_qos_remove_request - modifies an existing qos request
    > + * @pm_qos_req: handle to request list element
    > *
    > - * Will remove named qos request from pm_qos_class list of parameters and
    > - * recompute the current target value for the pm_qos_class.
    > + * Will remove pm qos request from the list of requests and
    > + * recompute the current target value for the pm_qos_class. Call this
    > + * on slow code paths.
    > */
    > -void pm_qos_remove_requirement(int pm_qos_class, char *name)
    > +void pm_qos_remove_request(struct pm_qos_request_list *pm_qos_req)
    > {
    > unsigned long flags;
    > - struct requirement_list *node;
    > - int pending_update = 0;
    > + int qos_class;
    > +
    > + if (pm_qos_req == NULL)
    > + return;
    > + /* silent return to keep pcm code cleaner */
    >
    > + qos_class = pm_qos_req->pm_qos_class;
    > spin_lock_irqsave(&pm_qos_lock, flags);
    > - list_for_each_entry(node,
    > - &pm_qos_array[pm_qos_class]->requirements.list, list) {
    > - if (strcmp(node->name, name) == 0) {
    > - kfree(node->name);
    > - list_del(&node->list);
    > - kfree(node);
    > - pending_update = 1;
    > - break;
    > - }
    > - }
    > + list_del(&pm_qos_req->list);
    > + kfree(pm_qos_req);
    > spin_unlock_irqrestore(&pm_qos_lock, flags);
    > - if (pending_update)
    > - update_target(pm_qos_class);
    > + update_target(qos_class);
    > }
    > -EXPORT_SYMBOL_GPL(pm_qos_remove_requirement);
    > +EXPORT_SYMBOL_GPL(pm_qos_remove_request);
    >
    > /**
    > * pm_qos_add_notifier - sets notification entry for changes to target value
    > @@ -313,7 +305,7 @@ EXPORT_SYMBOL_GPL(pm_qos_remove_requirement);
    > * will register the notifier into a notification chain that gets called
    > * upon changes to the pm_qos_class target value.
    > */
    > - int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
    > +int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
    > {
    > int retval;
    >
    > @@ -343,21 +335,16 @@ int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
    > }
    > EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
    >
    > -#define PID_NAME_LEN 32
    > -
    > static int pm_qos_power_open(struct inode *inode, struct file *filp)
    > {
    > - int ret;
    > long pm_qos_class;
    > - char name[PID_NAME_LEN];
    >
    > pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
    > if (pm_qos_class >= 0) {
    > - filp->private_data = (void *)pm_qos_class;
    > - snprintf(name, PID_NAME_LEN, "process_%d", current->pid);
    > - ret = pm_qos_add_requirement(pm_qos_class, name,
    > - PM_QOS_DEFAULT_VALUE);
    > - if (ret >= 0)
    > + filp->private_data = (void *) pm_qos_add_request(pm_qos_class,
    > + PM_QOS_DEFAULT_VALUE);
    > +
    > + if (filp->private_data)
    > return 0;
    > }
    > return -EPERM;
    > @@ -365,32 +352,40 @@ static int pm_qos_power_open(struct inode *inode, struct file *filp)
    >
    > static int pm_qos_power_release(struct inode *inode, struct file *filp)
    > {
    > - int pm_qos_class;
    > - char name[PID_NAME_LEN];
    > + struct pm_qos_request_list *req;
    >
    > - pm_qos_class = (long)filp->private_data;
    > - snprintf(name, PID_NAME_LEN, "process_%d", current->pid);
    > - pm_qos_remove_requirement(pm_qos_class, name);
    > + req = (struct pm_qos_request_list *)filp->private_data;
    > + pm_qos_remove_request(req);
    >
    > return 0;
    > }
    >
    > +
    > static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
    > size_t count, loff_t *f_pos)
    > {
    > s32 value;
    > - int pm_qos_class;
    > - char name[PID_NAME_LEN];
    > -
    > - pm_qos_class = (long)filp->private_data;
    > - if (count != sizeof(s32))
    > + int x;
    > + char ascii_value[11];
    > + struct pm_qos_request_list *pm_qos_req;
    > +
    > + if (count == sizeof(s32)) {
    > + if (copy_from_user(&value, buf, sizeof(s32)))
    > + return -EFAULT;
    > + } else if (count == 11) { /* len('0x12345678/0') */
    > + if (copy_from_user(ascii_value, buf, 11))
    > + return -EFAULT;
    > + x = sscanf(ascii_value, "%x", &value);
    > + if (x != 1)
    > + return -EINVAL;
    > + pr_debug(KERN_ERR "%s, %d, 0x%x\n", ascii_value, x, value);
    > + } else
    > return -EINVAL;
    > - if (copy_from_user(&value, buf, sizeof(s32)))
    > - return -EFAULT;
    > - snprintf(name, PID_NAME_LEN, "process_%d", current->pid);
    > - pm_qos_update_requirement(pm_qos_class, name, value);
    >
    > - return sizeof(s32);
    > + pm_qos_req = (struct pm_qos_request_list *)filp->private_data;
    > + pm_qos_update_request(pm_qos_req, value);
    > +
    > + return count;
    > }
    >
    >
    > diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
    > index 875c8de..88f95e7 100644
    > --- a/net/mac80211/mlme.c
    > +++ b/net/mac80211/mlme.c
    > @@ -495,7 +495,7 @@ void ieee80211_recalc_ps(struct ieee80211_local *local, s32 latency)
    > s32 beaconint_us;
    >
    > if (latency < 0)
    > - latency = pm_qos_requirement(PM_QOS_NETWORK_LATENCY);
    > + latency = pm_qos_request(PM_QOS_NETWORK_LATENCY);
    >
    > beaconint_us = ieee80211_tu_to_usec(
    > found->vif.bss_conf.beacon_int);
    > diff --git a/sound/core/pcm.c b/sound/core/pcm.c
    > index 0d428d0..cbe815d 100644
    > --- a/sound/core/pcm.c
    > +++ b/sound/core/pcm.c
    > @@ -648,9 +648,6 @@ int snd_pcm_new_stream(struct snd_pcm *pcm, int stream, int substream_count)
    > substream->number = idx;
    > substream->stream = stream;
    > sprintf(substream->name, "subdevice #%i", idx);
    > - snprintf(substream->latency_id, sizeof(substream->latency_id),
    > - "ALSA-PCM%d-%d%c%d", pcm->card->number, pcm->device,
    > - (stream ? 'c' : 'p'), idx);
    > substream->buffer_bytes_max = UINT_MAX;
    > if (prev == NULL)
    > pstr->substream = substream;
    > diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
    > index 20b5982..192dd40 100644
    > --- a/sound/core/pcm_native.c
    > +++ b/sound/core/pcm_native.c
    > @@ -484,11 +484,13 @@ static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
    > snd_pcm_timer_resolution_change(substream);
    > runtime->status->state = SNDRV_PCM_STATE_SETUP;
    >
    > - pm_qos_remove_requirement(PM_QOS_CPU_DMA_LATENCY,
    > - substream->latency_id);
    > + if (substream->latency_pm_qos_req) {
    > + pm_qos_remove_request(substream->latency_pm_qos_req);
    > + substream->latency_pm_qos_req = NULL;
    > + }
    > if ((usecs = period_to_usecs(runtime)) >= 0)
    > - pm_qos_add_requirement(PM_QOS_CPU_DMA_LATENCY,
    > - substream->latency_id, usecs);
    > + substream->latency_pm_qos_req = pm_qos_add_request(
    > + PM_QOS_CPU_DMA_LATENCY, usecs);
    > return 0;
    > _error:
    > /* hardware might be unuseable from this time,
    > @@ -543,8 +545,8 @@ static int snd_pcm_hw_free(struct snd_pcm_substream *substream)
    > if (substream->ops->hw_free)
    > result = substream->ops->hw_free(substream);
    > runtime->status->state = SNDRV_PCM_STATE_OPEN;
    > - pm_qos_remove_requirement(PM_QOS_CPU_DMA_LATENCY,
    > - substream->latency_id);
    > + pm_qos_remove_request(substream->latency_pm_qos_req);
    > + substream->latency_pm_qos_req = NULL;
    > return result;
    > }
    >
    >



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