* Arnd Bergmann | 2016-07-15 14:29:31 [+0200]:
Agreed, but it's hard for the compiler to figure that out. On mainline,
we have the same thing in drivers/tty/serial/8250/8250_port.c btw. Don't see the warning there.
we have this instead:
local_irq_save(flags); if (uap->port.sysrq) locked = 0; else if (oops_in_progress) locked = spin_trylock(&uap->port.lock); else spin_lock(&uap->port.lock);… if (locked) spin_unlock(&uap->port.lock); local_irq_restore(flags);
which looks like it's intentionally written to avoid the warning and was changed by Thomas in "tty/serial/pl011: Make the locking work on RT":
http://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit/dr...
Maybe there is another way to write this upstream that avoids the warning.
I don't see any other way around except for initializing flags upfront:
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -2161,18 +2161,17 @@ pl011_console_write(struct console *co, const char *s, unsigned int count) { struct uart_amba_port *uap = amba_ports[co->index]; unsigned int old_cr = 0, new_cr; - unsigned long flags; + unsigned long flags = 0; int locked = 1;
clk_enable(uap->clk);
- local_irq_save(flags); if (uap->port.sysrq) locked = 0; else if (oops_in_progress) - locked = spin_trylock(&uap->port.lock); + locked = spin_trylock_irqsave(&uap->port.lock, flags); else - spin_lock(&uap->port.lock); + spin_lock_irqsave(&uap->port.lock, flags);
/* * First save the CR then disable the interrupts @@ -2196,8 +2195,7 @@ pl011_console_write(struct console *co, const char *s, unsigned int count) pl011_write(old_cr, uap, REG_CR);
if (locked) - spin_unlock(&uap->port.lock); - local_irq_restore(flags); + spin_unlock_irqrestore(&uap->port.lock, flags);
clk_disable(uap->clk); }
Arnd
Sebastian