Messages in this thread | | | Date | Thu, 29 Apr 2004 11:58:30 +0200 | From | Pavel Machek <> | Subject | Re: locking in psmouse |
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Hi!
> > psmouse-base.c does not have any locking. For example psmouse_command > > could race with data coming from the mouse, resulting in problem. This > > should fix it. > > Although I am not arguing that locking might be needed in psmouse module I > am somewhat confused how it will help in case of data stream coming from the > mouse... If mouse sent a byte before the kernel issue a command then it will > be delivered by KBC controller and will be processed by the interrupt handler, > probably messing up detection process. That's why as soon as we decide that > the device behind PS/2 port is some kind of mouse we disable the stream mode.
Does that mean that mouse can not talk while we are sending commands to it? That would help a bit.
Anyway, locking still seems to be needed:
while (psmouse->cmdcnt && timeout--) {
if (psmouse->cmdcnt == 1 && command == PSMOUSE_CMD_RESET_BAT && timeout > 100000) /* do not run in a endless loop */ timeout = 100000; /* 1 sec */
if (psmouse->cmdcnt == 1 && command == PSMOUSE_CMD_GETID && psmouse->cmdbuf[1] != 0xab && psmouse->cmdbuf[1] != 0xac) { psmouse->cmdcnt = 0; break; }
spin_unlock_irq(&psmouse_lock); udelay(1); spin_lock_irq(&psmouse_lock); }
racing with
if (psmouse->cmdcnt) { psmouse->cmdbuf[--psmouse->cmdcnt] = data; goto out; }
now... if each runs on different CPU, it can be possible that psmouse->cmdcnt is seen as 1 but data are not yet in psmouse->cmdbuf... Locking seems neccessary here. Pavel -- 934a471f20d6580d5aad759bf0d97ddc - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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