Dear Alan,, Could you kindly help to explain more detail about "spin_unlock_irq " you mentioned? Thanks! Best Regards, soho 2011/6/7 Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>: > On Tue, 7 Jun 2011, Soho Soho123 wrote: > >> Dear Alan, >> >> We test again with 2 case: >> Case 1: without WiFi, just using ethernet interface for IP cam test. >> result: It can work for over night. >> hence, we may focus on WiFi driver. >> Case 2: we modify WiFi driver in TX direction. the function netdev->hard_xmit() >> originally, the function use:spin_lock_irqsave and >> spin_unlock_irqrestore for protection >> We modify the code : using spin_lock_irq and spin_unlock_irq to >> replace the original code. >> >> Then, the result is better. At least we can see IP cam can work for >> several hours. >> >> As we have known, in case 2, spin_lock_irq and spin_unlock_irq may >> cause irq loss, but it seems >> usb and wifi can work more smooth. > > It may lead to problems, though. spin_unlock_irq() may enable > interrupts at a time when they are supposed to remain disabled. > >> It seems the "irq count" is the cause of problem from the testing Case >> 1 &2. Since irq from WiFi is very much in the testing. >> >> if the Irq is so busy in the system that WiFi has included, then "usb >> irq will not be service at once" is sure. >> Do you have any idea? > > No, not really. You might want to post a question to people on the > linux-wireless mailing list. > >> And the question from Laurent, >> ."If the URB is resubmitted too late, why can't it just be queued for >> the next (micro-)frame " > > We _do_ queued it for the next microframe. But if the URB is > resubmitted _too_ late (i.e., more than 20 ms too late) then ehci-hcd > doesn't realize the URB is late -- it thinks the URB is very early! > > For example, suppose there are 512 frames in the periodic schedule. > Suppose the last URB ended in frame 500, so the next available slot is > frame 501. But suppose the next URB was submitted 40 ms too late, and > the current frame number is already 28 ( = 500 + 40 mod 512). > > Then ehci-hcd thinks the URB was submitted 473 ( = 501 - 28) frames > early, not 40 frames late. That's why you get errors. > > Alan Stern > > -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
