From 394668b4523a3bb88be279f1c11f812602d7971a Mon Sep 17 00:00:00 2001 From: Colin Cross Date: Wed, 31 Oct 2012 17:41:39 -0700 Subject: [PATCH] ARM: fiq_debugger: lock between tty and console writes debug_console_write calls debug_uart_flush, which will usually wait until the serial port fifo empties. If another thread is continuously calling fiq_tty_write, the fifo will constantly be refilled and debug_uart_flush might never return. Add a spinlock that is locked in debug_console_write and fiq_tty_write to ensure they can't run at the same time. This has an extra advantage of preventing lines from the console and tty from being mixed together. Also reduce the size returned by fiq_tty_write_room to keep the time spent with the spinlock held to a reasonable value. In addition, make sure fiq context can't loop forever by never calling debug_uart_flush when the console is enabled. Change-Id: I5712b01f740ca0c84f680d2032c9fa16b7656939 Signed-off-by: Colin Cross --- arch/arm/common/fiq_debugger.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/arch/arm/common/fiq_debugger.c b/arch/arm/common/fiq_debugger.c index a12810b5fb68..946a31403ce0 100644 --- a/arch/arm/common/fiq_debugger.c +++ b/arch/arm/common/fiq_debugger.c @@ -86,6 +86,7 @@ struct fiq_debugger_state { char work_cmd[DEBUG_MAX]; #ifdef CONFIG_FIQ_DEBUGGER_CONSOLE + spinlock_t console_lock; struct console console; struct tty_struct *tty; int tty_open_count; @@ -708,8 +709,9 @@ static bool debug_fiq_exec(struct fiq_debugger_state *state, state->no_sleep = true; debug_printf(state, "disabling sleep\n"); } else if (!strcmp(cmd, "console")) { - state->console_enable = true; debug_printf(state, "console mode\n"); + debug_uart_flush(state); + state->console_enable = true; } else if (!strcmp(cmd, "cpu")) { debug_printf(state, "cpu %d\n", state->current_cpu); } else if (!strncmp(cmd, "cpu ", 4)) { @@ -896,7 +898,8 @@ static bool debug_handle_uart_interrupt(struct fiq_debugger_state *state, } last_c = c; } - debug_uart_flush(state); + if (!state->console_enable) + debug_uart_flush(state); if (state->pdata->fiq_ack) state->pdata->fiq_ack(state->pdev, state->fiq); @@ -980,6 +983,7 @@ static void debug_console_write(struct console *co, const char *s, unsigned int count) { struct fiq_debugger_state *state; + unsigned long flags; state = container_of(co, struct fiq_debugger_state, console); @@ -987,12 +991,14 @@ static void debug_console_write(struct console *co, return; debug_uart_enable(state); + spin_lock_irqsave(&state->console_lock, flags); while (count--) { if (*s == '\n') debug_putc(state, '\r'); debug_putc(state, *s++); } debug_uart_flush(state); + spin_unlock_irqrestore(&state->console_lock, flags); debug_uart_disable(state); } @@ -1033,8 +1039,10 @@ int fiq_tty_write(struct tty_struct *tty, const unsigned char *buf, int count) return count; debug_uart_enable(state); + spin_lock_irq(&state->console_lock); for (i = 0; i < count; i++) debug_putc(state, *buf++); + spin_unlock_irq(&state->console_lock); debug_uart_disable(state); return count; @@ -1042,7 +1050,7 @@ int fiq_tty_write(struct tty_struct *tty, const unsigned char *buf, int count) int fiq_tty_write_room(struct tty_struct *tty) { - return 1024; + return 16; } #ifdef CONFIG_CONSOLE_POLL -- 2.20.1