On Wed, 31 Mar 2010 20:43:29 -0500 "Ambrose, Martin" <martin@xxxxxx> wrote: > > > + /* > > > + * Set flag to 0 and wait for isr to set to 1. It would seem there is a > > > + * race condition here where the ISR could have occured just before or > > > + * just after this set. But since we are just coarsely waiting for > > > + * a frame to complete then that's OK. i.e. if the frame completed > > > + * just before this code executed then we have to wait another full > > > + * frame time but there is no way to avoid such a situation. On the > > > + * other hand if the frame completed just after then we don't need > > > + * to wait long at all. Either way we are guaranteed to return to the > > > + * user immediately after a frame completion which is all that is > > > + * required. > > > + */ > > > + par->vsync_flag = 0; > > > + ret = wait_event_interruptible_timeout(par->vsync_wait, > > > + par->vsync_flag != 0, > > > + par->vsync_timeout); > > > > If the calling process has signal_pending() (say, someone hit ^C) then > > wait_event_interruptible_timeout() will fall straight through with > > -ERESTARTSYS. Will this cause the driver to malfunction at all? > > I don't think so since the driver doesn't make use of this > information in any way. This is just status to the caller that the > current frame has finished DMA'ing out of the framebuffer. > > Could you maybe propose a scenario/use case where you think it is > problematic? I could then either reason why it should be OK or > I'll create a test harness and see how the driver can/should be modified. > Gee, I dunno - I don't understand the driver to that level. If you're OK with this wait being interrupted by a signal and the driver handles it OK then fine, that's a feature. To test it I suppose you should give your test app a signal handler and blast kills at it from another process. -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
