[PATCH v3 05/12] OMAP: Serial: Hold console lock for console usage.
From: Kevin Hilman <hidden>
Date: 2011-06-25 00:06:30
Also in:
linux-omap, linux-serial
Possibly related (same subject, not in this thread)
- 2011-06-27 · [PATCH v3 05/12] OMAP: Serial: Hold console lock for console usage. · Kevin Hilman <hidden>
- 2011-06-08 · [PATCH v3 05/12] OMAP: Serial: Hold console lock for console usage. · Govindraj.R <hidden>
"Govindraj.R" [off-list ref] writes:
quoted hunk
Acquire console lock before enabling and writing to console-uart to avoid any recursive prints from console write. for ex: --> printk --> uart_console_write --> get_sync --> printk from omap_device enable --> uart_console write Use RPM_SUSPENDING check to avoid below scenario during bootup As during bootup console_lock is not available. --> uart_add_one_port --> console_register --> console_lock --> console_unlock --> call_console_drivers (here yet console_lock is not released) --> uart_console_write Acked-by: Alan Cox <redacted> Signed-off-by: Govindraj.R <redacted> --- drivers/tty/serial/omap-serial.c | 20 +++++++++++++++++++- 1 files changed, 19 insertions(+), 1 deletions(-)diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c index 897416f..ee94291 100644 --- a/drivers/tty/serial/omap-serial.c +++ b/drivers/tty/serial/omap-serial.c@@ -1008,7 +1008,22 @@ serial_omap_console_write(struct console *co, const char *s, struct uart_omap_port *up = serial_omap_console_ports[co->index]; unsigned long flags; unsigned int ier; - int locked = 1; + int console_lock = 0, locked = 1; + + if (console_trylock()) + console_lock = 1;
So now we take the console lock on *every* console write? Even if the device is not about to be idled? This is rather over-protective, don't you think?
+ /* + * If console_lock is not available and we are in suspending + * state then we can avoid the console usage scenario
s/in suspending state/runtime suspending/
+ * as this may introduce recursive prints. + * Basically this scenario occurs during boot while + * printing debug bootlogs.
The exact scenario for triggering this still not well described, and thus still I don't get it. I still don't fully understand this problem, but if it's isolated to runtime suspending, maybe you need a console lock in the runtime_suspend path (like you already have in the static suspend path.)
+ */ + + if (!console_lock && + up->pdev->dev.power.runtime_status == RPM_SUSPENDING) + return;
Assuming this was a printk, it's now lost, right? Not sure that's an acceptable solution.
quoted hunk
local_irq_save(flags); if (up->port.sysrq)@@ -1044,6 +1059,9 @@ serial_omap_console_write(struct console *co, const char *s, if (up->msr_saved_flags) check_modem_status(up); + if (console_lock) + console_unlock(); + serial_omap_port_disable(up); if (locked) spin_unlock(&up->port.lock);
Kevin