[PATCH linux dev-4.10 11/16] fsi: sbefifo: Switch list_lock from spinlock to mutex
Andrew Jeffery
andrew at aj.id.au
Thu Feb 15 23:36:01 AEDT 2018
We allocate GFP_KERNEL memory for a list element in sbefifo_enq_xfr() (elided
from the stack trace presumably by inlining) but do so under list_lock, which
was previously a spin lock. Enabling lock debugging gives the following
warning:
[ 188.830000] BUG: sleeping function called from invalid context at mm/slab.h:408
[ 188.830000] in_atomic(): 1, irqs_disabled(): 128, pid: 110, name: kworker/u2:9
[ 188.830000] INFO: lockdep is turned off.
[ 188.830000] irq event stamp: 9002
[ 188.830000] hardirqs last enabled at (9001): [<801105bc>] kmem_cache_alloc_trace+0x8c/0x284
[ 188.830000] hardirqs last disabled at (9002): [<8049458c>] _raw_spin_lock_irqsave+0x2c/0xa0
[ 188.830000] softirqs last enabled at (5370): [<8000987c>] __do_softirq+0x38c/0x510
[ 188.830000] softirqs last disabled at (5363): [<8001f154>] irq_exit+0x120/0x16c
[ 188.830000] CPU: 0 PID: 110 Comm: kworker/u2:9 Tainted: G W 4.10.17-00534-gb846201e7a2d #2277
[ 188.830000] Hardware name: ASpeed SoC
[ 188.830000] Workqueue: occ occ_worker
[ 188.830000] [<800108f8>] (unwind_backtrace) from [<8000e02c>] (show_stack+0x20/0x24)
[ 188.830000] [<8000e02c>] (show_stack) from [<8022d1c0>] (dump_stack+0x20/0x28)
[ 188.830000] [<8022d1c0>] (dump_stack) from [<80048bf8>] (___might_sleep+0x174/0x2ac)
[ 188.830000] [<80048bf8>] (___might_sleep) from [<80048da0>] (__might_sleep+0x70/0xb0)
[ 188.830000] [<80048da0>] (__might_sleep) from [<801106f8>] (kmem_cache_alloc_trace+0x1c8/0x284)
[ 188.830000] [<801106f8>] (kmem_cache_alloc_trace) from [<803330e8>] (sbefifo_write_common+0x228/0x4b4)
[ 188.830000] [<803330e8>] (sbefifo_write_common) from [<80333740>] (sbefifo_drv_write+0x24/0x28)
[ 188.830000] [<80333740>] (sbefifo_drv_write) from [<80333b58>] (occ_write_sbefifo+0x44/0x60)
[ 188.830000] [<80333b58>] (occ_write_sbefifo) from [<80334530>] (occ_worker+0x38/0x4a0)
[ 188.830000] [<80334530>] (occ_worker) from [<80034a2c>] (process_one_work+0x23c/0x6d4)
[ 188.830000] [<80034a2c>] (process_one_work) from [<80034f08>] (worker_thread+0x44/0x528)
[ 188.830000] [<80034f08>] (worker_thread) from [<8003c8c0>] (kthread+0x160/0x17c)
[ 188.830000] [<8003c8c0>] (kthread) from [<8000a888>] (ret_from_fork+0x14/0x2c)
Avoid the warning (or using GFP_ATOMIC memory) by switching to a mutex, as we
only require mutual exclusion, not pre-emption be disabled (occ_worker() is
executed on a workqueue). This should also reduce the latency impact of calling
into the OCC.
Signed-off-by: Andrew Jeffery <andrew at aj.id.au>
---
drivers/fsi/fsi-sbefifo.c | 35 ++++++++++++++++-------------------
1 file changed, 16 insertions(+), 19 deletions(-)
diff --git a/drivers/fsi/fsi-sbefifo.c b/drivers/fsi/fsi-sbefifo.c
index 7b3c7a22b4a2..27df244c8930 100644
--- a/drivers/fsi/fsi-sbefifo.c
+++ b/drivers/fsi/fsi-sbefifo.c
@@ -67,7 +67,7 @@ struct sbefifo {
wait_queue_head_t wait;
struct list_head xfrs;
struct kref kref;
- spinlock_t list_lock; /* lock access to the xfrs list */
+ struct mutex list_lock; /* lock access to the xfrs list */
struct mutex sbefifo_lock; /* lock access to the hardware */
char name[32];
int idx;
@@ -399,12 +399,11 @@ static void sbefifo_worker(struct work_struct *work)
int ret = 0;
u32 sts;
int i;
- unsigned long flags;
- spin_lock_irqsave(&sbefifo->list_lock, flags);
+ mutex_lock(&sbefifo->list_lock);
xfr = list_first_entry_or_null(&sbefifo->xfrs, struct sbefifo_xfr,
xfrs);
- spin_unlock_irqrestore(&sbefifo->list_lock, flags);
+ mutex_unlock(&sbefifo->list_lock);
if (!xfr)
return;
@@ -516,9 +515,9 @@ static void sbefifo_worker(struct work_struct *work)
set_bit(SBEFIFO_XFR_COMPLETE, &xfr->flags);
- spin_lock_irqsave(&sbefifo->list_lock, flags);
+ mutex_lock(&sbefifo->list_lock);
list_del(&xfr->xfrs);
- spin_unlock_irqrestore(&sbefifo->list_lock, flags);
+ mutex_unlock(&sbefifo->list_lock);
if (unlikely(test_bit(SBEFIFO_XFR_CANCEL,
&xfr->flags)))
@@ -535,17 +534,17 @@ static void sbefifo_worker(struct work_struct *work)
dev_err(&sbefifo->fsi_dev->dev,
"Fatal bus access failure: %d\n", ret);
- spin_lock_irqsave(&sbefifo->list_lock, flags);
+ mutex_lock(&sbefifo->list_lock);
list_for_each_entry_safe(xfr, tmp, &sbefifo->xfrs, xfrs) {
list_del(&xfr->xfrs);
kfree(xfr);
}
INIT_LIST_HEAD(&sbefifo->xfrs);
- spin_unlock_irqrestore(&sbefifo->list_lock, flags);
+ mutex_unlock(&sbefifo->list_lock);
} else if (eot) {
- spin_lock_irqsave(&sbefifo->list_lock, flags);
+ mutex_lock(&sbefifo->list_lock);
xfr = sbefifo_next_xfr(sbefifo);
- spin_unlock_irqrestore(&sbefifo->list_lock, flags);
+ mutex_unlock(&sbefifo->list_lock);
if (xfr) {
wake_up_interruptible(&sbefifo->wait);
@@ -717,7 +716,6 @@ static ssize_t sbefifo_write_common(struct sbefifo_client *client,
struct sbefifo_xfr *xfr;
ssize_t ret = 0;
size_t n;
- unsigned long flags;
if ((len >> 2) << 2 != len)
return -EINVAL;
@@ -728,26 +726,26 @@ static ssize_t sbefifo_write_common(struct sbefifo_client *client,
sbefifo_get_client(client);
n = sbefifo_buf_nbwriteable(&client->wbuf);
- spin_lock_irqsave(&sbefifo->list_lock, flags);
+ mutex_lock(&sbefifo->list_lock);
/* next xfr to be executed */
xfr = list_first_entry_or_null(&sbefifo->xfrs, struct sbefifo_xfr,
xfrs);
if ((client->f_flags & O_NONBLOCK) && xfr && n < len) {
- spin_unlock_irqrestore(&sbefifo->list_lock, flags);
+ mutex_unlock(&sbefifo->list_lock);
ret = -EAGAIN;
goto out;
}
xfr = sbefifo_enq_xfr(client); /* this xfr queued up */
if (IS_ERR(xfr)) {
- spin_unlock_irqrestore(&sbefifo->list_lock, flags);
+ mutex_unlock(&sbefifo->list_lock);
ret = PTR_ERR(xfr);
goto out;
}
- spin_unlock_irqrestore(&sbefifo->list_lock, flags);
+ mutex_unlock(&sbefifo->list_lock);
/*
* Partial writes are not really allowed in that EOT is sent exactly
@@ -958,7 +956,7 @@ static int sbefifo_probe(struct device *dev)
}
}
- spin_lock_init(&sbefifo->list_lock);
+ mutex_init(&sbefifo->list_lock);
mutex_init(&sbefifo->sbefifo_lock);
kref_init(&sbefifo->kref);
init_waitqueue_head(&sbefifo->wait);
@@ -1002,11 +1000,10 @@ static int sbefifo_remove(struct device *dev)
{
struct sbefifo *sbefifo = dev_get_drvdata(dev);
struct sbefifo_xfr *xfr, *tmp;
- unsigned long flags;
/* lock the sbefifo so to prevent deleting an ongoing xfr */
mutex_lock(&sbefifo->sbefifo_lock);
- spin_lock_irqsave(&sbefifo->list_lock, flags);
+ mutex_lock(&sbefifo->list_lock);
WRITE_ONCE(sbefifo->rc, -ENODEV);
list_for_each_entry_safe(xfr, tmp, &sbefifo->xfrs, xfrs) {
@@ -1016,7 +1013,7 @@ static int sbefifo_remove(struct device *dev)
INIT_LIST_HEAD(&sbefifo->xfrs);
- spin_unlock_irqrestore(&sbefifo->list_lock, flags);
+ mutex_unlock(&sbefifo->list_lock);
mutex_unlock(&sbefifo->sbefifo_lock);
wake_up_all(&sbefifo->wait);
--
2.14.1
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