The refcount_* APIs are designed to address known issues with the
atomic_t APIs for reference counting. They protect the reference
counters from overflow/underflow, use-after-free errors, provide
improved memory ordering guarantee schemes, are neater and safer.
Hence, replace the atomic_* APIs by their equivalent refcount_t
API functions.
This patch proposal address the following warnings generated by
the atomic_as_refcounter.cocci coccinelle script
atomic_add_return(-1, ...)
Signed-off-by: Deepak R Varma <[email protected]>
---
Note: The patch is compile tested using dec_station.defconfig for
MIPS architecture.
drivers/tty/serial/dz.c | 34 +++++++++++++---------------------
drivers/tty/serial/zs.c | 11 ++++-------
drivers/tty/serial/zs.h | 2 +-
3 files changed, 18 insertions(+), 29 deletions(-)
diff --git a/drivers/tty/serial/dz.c b/drivers/tty/serial/dz.c
index 6b7ed7f2f3ca..c248201f9499 100644
--- a/drivers/tty/serial/dz.c
+++ b/drivers/tty/serial/dz.c
@@ -46,7 +46,7 @@
#include <linux/tty.h>
#include <linux/tty_flip.h>
-#include <linux/atomic.h>
+#include <linux/refcount.h>
#include <linux/io.h>
#include <asm/bootinfo.h>
@@ -75,8 +75,8 @@ struct dz_port {
struct dz_mux {
struct dz_port dport[DZ_NB_PORT];
- atomic_t map_guard;
- atomic_t irq_guard;
+ refcount_t map_guard;
+ refcount_t irq_guard;
int initialised;
};
@@ -399,18 +399,17 @@ static int dz_startup(struct uart_port *uport)
struct dz_port *dport = to_dport(uport);
struct dz_mux *mux = dport->mux;
unsigned long flags;
- int irq_guard;
int ret;
u16 tmp;
- irq_guard = atomic_add_return(1, &mux->irq_guard);
- if (irq_guard != 1)
+ refcount_inc(&mux->irq_guard);
+ if (refcount_read(&mux->irq_guard) != 1)
return 0;
ret = request_irq(dport->port.irq, dz_interrupt,
IRQF_SHARED, "dz", mux);
if (ret) {
- atomic_add(-1, &mux->irq_guard);
+ refcount_dec(&mux->irq_guard);
printk(KERN_ERR "dz: Cannot get IRQ %d!\n", dport->port.irq);
return ret;
}
@@ -440,15 +439,13 @@ static void dz_shutdown(struct uart_port *uport)
struct dz_port *dport = to_dport(uport);
struct dz_mux *mux = dport->mux;
unsigned long flags;
- int irq_guard;
u16 tmp;
spin_lock_irqsave(&dport->port.lock, flags);
dz_stop_tx(&dport->port);
spin_unlock_irqrestore(&dport->port.lock, flags);
- irq_guard = atomic_add_return(-1, &mux->irq_guard);
- if (!irq_guard) {
+ if (refcount_dec_and_test(&mux->irq_guard)) {
/* Disable interrupts. */
tmp = dz_in(dport, DZ_CSR);
tmp &= ~(DZ_RIE | DZ_TIE);
@@ -662,13 +659,11 @@ static const char *dz_type(struct uart_port *uport)
static void dz_release_port(struct uart_port *uport)
{
struct dz_mux *mux = to_dport(uport)->mux;
- int map_guard;
iounmap(uport->membase);
uport->membase = NULL;
- map_guard = atomic_add_return(-1, &mux->map_guard);
- if (!map_guard)
+ if (refcount_dec_and_test(&mux->map_guard))
release_mem_region(uport->mapbase, dec_kn_slot_size);
}
@@ -687,14 +682,12 @@ static int dz_map_port(struct uart_port *uport)
static int dz_request_port(struct uart_port *uport)
{
struct dz_mux *mux = to_dport(uport)->mux;
- int map_guard;
int ret;
- map_guard = atomic_add_return(1, &mux->map_guard);
- if (map_guard == 1) {
- if (!request_mem_region(uport->mapbase, dec_kn_slot_size,
- "dz")) {
- atomic_add(-1, &mux->map_guard);
+ refcount_inc(&mux->map_guard);
+ if (refcount_read(&mux->map_guard) == 1) {
+ if (!request_mem_region(uport->mapbase, dec_kn_slot_size, "dz")) {
+ refcount_dec(&mux->map_guard);
printk(KERN_ERR
"dz: Unable to reserve MMIO resource\n");
return -EBUSY;
@@ -702,8 +695,7 @@ static int dz_request_port(struct uart_port *uport)
}
ret = dz_map_port(uport);
if (ret) {
- map_guard = atomic_add_return(-1, &mux->map_guard);
- if (!map_guard)
+ if (refcount_dec_and_test(&mux->map_guard))
release_mem_region(uport->mapbase, dec_kn_slot_size);
return ret;
}
diff --git a/drivers/tty/serial/zs.c b/drivers/tty/serial/zs.c
index 730c648e32ff..6fa79705a0c9 100644
--- a/drivers/tty/serial/zs.c
+++ b/drivers/tty/serial/zs.c
@@ -753,15 +753,14 @@ static int zs_startup(struct uart_port *uport)
struct zs_port *zport = to_zport(uport);
struct zs_scc *scc = zport->scc;
unsigned long flags;
- int irq_guard;
int ret;
- irq_guard = atomic_add_return(1, &scc->irq_guard);
- if (irq_guard == 1) {
+ refcount_inc(&scc->irq_guard);
+ if (refcount_read(&scc->irq_guard) == 1) {
ret = request_irq(zport->port.irq, zs_interrupt,
IRQF_SHARED, "scc", scc);
if (ret) {
- atomic_add(-1, &scc->irq_guard);
+ refcount_dec(&scc->irq_guard);
printk(KERN_ERR "zs: can't get irq %d\n",
zport->port.irq);
return ret;
@@ -806,7 +805,6 @@ static void zs_shutdown(struct uart_port *uport)
struct zs_port *zport = to_zport(uport);
struct zs_scc *scc = zport->scc;
unsigned long flags;
- int irq_guard;
spin_lock_irqsave(&scc->zlock, flags);
@@ -816,8 +814,7 @@ static void zs_shutdown(struct uart_port *uport)
spin_unlock_irqrestore(&scc->zlock, flags);
- irq_guard = atomic_add_return(-1, &scc->irq_guard);
- if (!irq_guard)
+ if (refcount_dec_and_test(&scc->irq_guard))
free_irq(zport->port.irq, scc);
}
diff --git a/drivers/tty/serial/zs.h b/drivers/tty/serial/zs.h
index 26ef8eafa1c1..bd97b73d7e16 100644
--- a/drivers/tty/serial/zs.h
+++ b/drivers/tty/serial/zs.h
@@ -40,7 +40,7 @@ struct zs_port {
struct zs_scc {
struct zs_port zport[2];
spinlock_t zlock;
- atomic_t irq_guard;
+ refcount_t irq_guard;
int initialised;
};
--
2.34.1
On Thu, Dec 22, 2022 at 01:27:40AM +0530, Deepak R Varma wrote:
> The refcount_* APIs are designed to address known issues with the
> atomic_t APIs for reference counting. They protect the reference
> counters from overflow/underflow, use-after-free errors, provide
> improved memory ordering guarantee schemes, are neater and safer.
> Hence, replace the atomic_* APIs by their equivalent refcount_t
> API functions.
>
> This patch proposal address the following warnings generated by
> the atomic_as_refcounter.cocci coccinelle script
> atomic_add_return(-1, ...)
>
>
> Signed-off-by: Deepak R Varma <[email protected]>
> ---
> Note: The patch is compile tested using dec_station.defconfig for
> MIPS architecture.
Do you have this hardware? If not, please just do
one-variable-at-a-time so that if there are real problems, we can revert
the offending change easier. And it makes it simpler to review.
But, are you sure this is correct:
> - irq_guard = atomic_add_return(1, &mux->irq_guard);
> - if (irq_guard != 1)
> + refcount_inc(&mux->irq_guard);
> + if (refcount_read(&mux->irq_guard) != 1)
That is now different logic than before, why? Are you sure this is ok?
I stopped reviewing here...
thanks,
greg k-h
On Thu, Dec 22, 2022 at 06:55:01AM +0100, Greg Kroah-Hartman wrote:
> On Thu, Dec 22, 2022 at 01:27:40AM +0530, Deepak R Varma wrote:
> > The refcount_* APIs are designed to address known issues with the
> > atomic_t APIs for reference counting. They protect the reference
> > counters from overflow/underflow, use-after-free errors, provide
> > improved memory ordering guarantee schemes, are neater and safer.
> > Hence, replace the atomic_* APIs by their equivalent refcount_t
> > API functions.
> >
> > This patch proposal address the following warnings generated by
> > the atomic_as_refcounter.cocci coccinelle script
> > atomic_add_return(-1, ...)
> >
> >
> > Signed-off-by: Deepak R Varma <[email protected]>
> > ---
> > Note: The patch is compile tested using dec_station.defconfig for
> > MIPS architecture.
>
> Do you have this hardware? If not, please just do
> one-variable-at-a-time so that if there are real problems, we can revert
> the offending change easier. And it makes it simpler to review.
Hi Greg,
I do not have the hardware. I will make a one variable per patch change as
suggest and send in a patch set.
>
> But, are you sure this is correct:
>
> > - irq_guard = atomic_add_return(1, &mux->irq_guard);
> > - if (irq_guard != 1)
> > + refcount_inc(&mux->irq_guard);
> > + if (refcount_read(&mux->irq_guard) != 1)
>
> That is now different logic than before, why? Are you sure this is ok?
This is not correct. I read it wrong. I will correct this in the patch set.
>
> I stopped reviewing here...
Thanks. I will review the rest of the changes per your advise and make the
corrections.
regards,
./drv
>
> thanks,
>
> greg k-h