Messages in this thread Patch in this message |  | | Date | Sat, 24 Dec 2022 13:47:12 +0530 | From | Deepak R Varma <> | Subject | [PATCH v2] tty: serial: dz: convert atomic_* to refcount_* APIs for irq_guard |
| |
The refcount_* APIs are designed to address known issues with the atomic_t APIs for reference counting. They provide following distinct advantages: - protect the reference counters from overflow/underflow - avoid use-after-free errors - provide improved memory ordering guarantee schemes - 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 <drv@mailo.com> ---
Changes in v2: 1. Separate the combined change into one variable per patch as suggested by gregkh@linuxfoundation.org 2. There was additional feedback on validating the change as it appeared to modify the existing logic. However, I found that the logic does not change with the proposed refcount_* APIs used in this change. Hence that feedback is not applied in this version.
Please Note: The patch is compile tested using dec_station.defconfig for MIPS architecture.
drivers/tty/serial/dz.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-)
diff --git a/drivers/tty/serial/dz.c b/drivers/tty/serial/dz.c index b70edc248f8b..0aa59a9beeb7 100644 --- a/drivers/tty/serial/dz.c +++ b/drivers/tty/serial/dz.c @@ -46,7 +46,6 @@ #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> @@ -77,7 +76,7 @@ struct dz_port { struct dz_mux { struct dz_port dport[DZ_NB_PORT]; refcount_t map_guard; - atomic_t irq_guard; + refcount_t irq_guard; int initialised; };
@@ -400,18 +399,16 @@ 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); + 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; } @@ -441,15 +438,13 @@ 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); -- 2.34.1
|  |