Re: [PATCH 1/9] macintosh/via-macii: Access autopoll_devs when inside lock
From: Guenter Roeck <linux@roeck-us.net>
Date: 2020-08-09 19:01:45
Also in:
linux-m68k, lkml
Hi, On Sun, Jun 28, 2020 at 02:23:12PM +1000, Finn Thain wrote:
The interrupt handler should be excluded when accessing the autopoll_devs variable.
I am quite baffled by this patch. Other than adding an unnecessary lock / unlock sequence, accessing a variable (which is derived from another variable) from inside or outside a lock does not make a difference. If autopoll_devs = devs & 0xfffe is 0 inside the lock, it will just as much be 0 outside the lock, and vice versa. Can you explain this in some more detail ? Not that is matters much since the change already made it into mainline, but I would like to understand what if anything I am missing here. Thanks, Guenter
quoted hunk ↗ jump to hunk
Fixes: d95fd5fce88f0 ("m68k: Mac II ADB fixes") # v5.0+ Tested-by: Stan Johnson <redacted> Signed-off-by: Finn Thain <redacted> --- drivers/macintosh/via-macii.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-)diff --git a/drivers/macintosh/via-macii.c b/drivers/macintosh/via-macii.c index ac824d7b2dcfc..6aa903529570d 100644 --- a/drivers/macintosh/via-macii.c +++ b/drivers/macintosh/via-macii.c@@ -270,15 +270,12 @@ static int macii_autopoll(int devs) unsigned long flags; int err = 0; + local_irq_save(flags); + /* bit 1 == device 1, and so on. */ autopoll_devs = devs & 0xFFFE; - if (!autopoll_devs) - return 0; - - local_irq_save(flags); - - if (current_req == NULL) { + if (autopoll_devs && !current_req) { /* Send a Talk Reg 0. The controller will repeatedly transmit * this as long as it is idle. */