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Date: Thu, 22 Dec 2022 01:27:40 +0530 From: Deepak R Varma <drv@...lo.com> To: "Maciej W. Rozycki" <macro@...am.me.uk>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>, linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org Cc: Saurabh Singh Sengar <ssengar@...rosoft.com>, Praveen Kumar <kumarpraveen@...ux.microsoft.com>, drv@...lo.com Subject: [PATCH] tty: serial: convert atomic_* to refcount_* APIs 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 <drv@...lo.com> --- 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
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