[ Upstream commit 09f11b6c99feaf86a26444bca85dc693b3f58f8b ]
switch_lock was introduced because it allowed serialization of device authorization requests from userspace without need to take the big domain lock (tb->lock). This was fine because device authorization with ICM is just one command that is sent to the firmware. Now that we start to handle all tunneling in the driver switch_lock is not enough because we need to walk over the topology to establish paths.
For this reason drop switch_lock from the driver completely in favour of big domain lock.
There is one complication, though. If userspace is waiting for the lock in tb_switch_set_authorized(), it keeps the device_del() from removing the sysfs attribute because it waits for active users to release the attribute first which leads into following splat:
INFO: task kworker/u8:3:73 blocked for more than 61 seconds. Tainted: G W 5.1.0-rc1+ #244 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/u8:3 D12976 73 2 0x80000000 Workqueue: thunderbolt0 tb_handle_hotplug [thunderbolt] Call Trace: ? __schedule+0x2e5/0x740 ? _raw_spin_lock_irqsave+0x12/0x40 ? prepare_to_wait_event+0xc5/0x160 schedule+0x2d/0x80 __kernfs_remove.part.17+0x183/0x1f0 ? finish_wait+0x80/0x80 kernfs_remove_by_name_ns+0x4a/0x90 remove_files.isra.1+0x2b/0x60 sysfs_remove_group+0x38/0x80 sysfs_remove_groups+0x24/0x40 device_remove_attrs+0x3d/0x70 device_del+0x14c/0x360 device_unregister+0x15/0x50 tb_switch_remove+0x9e/0x1d0 [thunderbolt] tb_handle_hotplug+0x119/0x5a0 [thunderbolt] ? process_one_work+0x1b7/0x420 process_one_work+0x1b7/0x420 worker_thread+0x37/0x380 ? _raw_spin_unlock_irqrestore+0xf/0x30 ? process_one_work+0x420/0x420 kthread+0x118/0x130 ? kthread_create_on_node+0x60/0x60 ret_from_fork+0x35/0x40
We deal this by following what network stack did for some of their attributes and use mutex_trylock() with restart_syscall(). This makes userspace release the attribute allowing sysfs attribute removal to progress before the write is restarted and eventually fail when the attribute is removed.
Signed-off-by: Mika Westerberg mika.westerberg@linux.intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/thunderbolt/switch.c | 45 +++++++++++++++--------------------- drivers/thunderbolt/tb.h | 3 +-- 2 files changed, 20 insertions(+), 28 deletions(-)
diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c index cd96994dc0947..32e012713dbeb 100644 --- a/drivers/thunderbolt/switch.c +++ b/drivers/thunderbolt/switch.c @@ -10,15 +10,13 @@ #include <linux/idr.h> #include <linux/nvmem-provider.h> #include <linux/pm_runtime.h> +#include <linux/sched/signal.h> #include <linux/sizes.h> #include <linux/slab.h> #include <linux/vmalloc.h>
#include "tb.h"
-/* Switch authorization from userspace is serialized by this lock */ -static DEFINE_MUTEX(switch_lock); - /* Switch NVM support */
#define NVM_DEVID 0x05 @@ -254,8 +252,8 @@ static int tb_switch_nvm_write(void *priv, unsigned int offset, void *val, struct tb_switch *sw = priv; int ret = 0;
- if (mutex_lock_interruptible(&switch_lock)) - return -ERESTARTSYS; + if (!mutex_trylock(&sw->tb->lock)) + return restart_syscall();
/* * Since writing the NVM image might require some special steps, @@ -275,7 +273,7 @@ static int tb_switch_nvm_write(void *priv, unsigned int offset, void *val, memcpy(sw->nvm->buf + offset, val, bytes);
unlock: - mutex_unlock(&switch_lock); + mutex_unlock(&sw->tb->lock);
return ret; } @@ -364,10 +362,7 @@ static int tb_switch_nvm_add(struct tb_switch *sw) } nvm->non_active = nvm_dev;
- mutex_lock(&switch_lock); sw->nvm = nvm; - mutex_unlock(&switch_lock); - return 0;
err_nvm_active: @@ -384,10 +379,8 @@ static void tb_switch_nvm_remove(struct tb_switch *sw) { struct tb_switch_nvm *nvm;
- mutex_lock(&switch_lock); nvm = sw->nvm; sw->nvm = NULL; - mutex_unlock(&switch_lock);
if (!nvm) return; @@ -716,8 +709,8 @@ static int tb_switch_set_authorized(struct tb_switch *sw, unsigned int val) { int ret = -EINVAL;
- if (mutex_lock_interruptible(&switch_lock)) - return -ERESTARTSYS; + if (!mutex_trylock(&sw->tb->lock)) + return restart_syscall();
if (sw->authorized) goto unlock; @@ -760,7 +753,7 @@ static int tb_switch_set_authorized(struct tb_switch *sw, unsigned int val) }
unlock: - mutex_unlock(&switch_lock); + mutex_unlock(&sw->tb->lock); return ret; }
@@ -817,15 +810,15 @@ static ssize_t key_show(struct device *dev, struct device_attribute *attr, struct tb_switch *sw = tb_to_switch(dev); ssize_t ret;
- if (mutex_lock_interruptible(&switch_lock)) - return -ERESTARTSYS; + if (!mutex_trylock(&sw->tb->lock)) + return restart_syscall();
if (sw->key) ret = sprintf(buf, "%*phN\n", TB_SWITCH_KEY_SIZE, sw->key); else ret = sprintf(buf, "\n");
- mutex_unlock(&switch_lock); + mutex_unlock(&sw->tb->lock); return ret; }
@@ -842,8 +835,8 @@ static ssize_t key_store(struct device *dev, struct device_attribute *attr, else if (hex2bin(key, buf, sizeof(key))) return -EINVAL;
- if (mutex_lock_interruptible(&switch_lock)) - return -ERESTARTSYS; + if (!mutex_trylock(&sw->tb->lock)) + return restart_syscall();
if (sw->authorized) { ret = -EBUSY; @@ -858,7 +851,7 @@ static ssize_t key_store(struct device *dev, struct device_attribute *attr, } }
- mutex_unlock(&switch_lock); + mutex_unlock(&sw->tb->lock); return ret; } static DEVICE_ATTR(key, 0600, key_show, key_store); @@ -904,8 +897,8 @@ static ssize_t nvm_authenticate_store(struct device *dev, bool val; int ret;
- if (mutex_lock_interruptible(&switch_lock)) - return -ERESTARTSYS; + if (!mutex_trylock(&sw->tb->lock)) + return restart_syscall();
/* If NVMem devices are not yet added */ if (!sw->nvm) { @@ -953,7 +946,7 @@ static ssize_t nvm_authenticate_store(struct device *dev, }
exit_unlock: - mutex_unlock(&switch_lock); + mutex_unlock(&sw->tb->lock);
if (ret) return ret; @@ -967,8 +960,8 @@ static ssize_t nvm_version_show(struct device *dev, struct tb_switch *sw = tb_to_switch(dev); int ret;
- if (mutex_lock_interruptible(&switch_lock)) - return -ERESTARTSYS; + if (!mutex_trylock(&sw->tb->lock)) + return restart_syscall();
if (sw->safe_mode) ret = -ENODATA; @@ -977,7 +970,7 @@ static ssize_t nvm_version_show(struct device *dev, else ret = sprintf(buf, "%x.%x\n", sw->nvm->major, sw->nvm->minor);
- mutex_unlock(&switch_lock); + mutex_unlock(&sw->tb->lock);
return ret; } diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h index 52584c4003e3a..f5e0282225d1c 100644 --- a/drivers/thunderbolt/tb.h +++ b/drivers/thunderbolt/tb.h @@ -80,8 +80,7 @@ struct tb_switch_nvm { * @depth: Depth in the chain this switch is connected (ICM only) * * When the switch is being added or removed to the domain (other - * switches) you need to have domain lock held. For switch authorization - * internal switch_lock is enough. + * switches) you need to have domain lock held. */ struct tb_switch { struct device dev;