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    usb: subtle increased memory usage in u_serial · 28609d40
    Jim Sung 提交于
    OK, the USB gadget serial driver actually has a couple of problems.  On
    gs_open(), it always allocates and queues an additional QUEUE_SIZE (16)
    worth of requests, so with a loop like this:
    
        i=1 ; while echo $i > /dev/ttyGS0 ; do let i++ ; done
    
    eventually we run into OOM (Out of Memory).
    
    Technically, it is not a leak as everything gets freed up when the USB
    connection is broken, but not on gs_close().
    
    With a USB device/gadget controller driver that has limited resources
    (e.g., Marvell has a this MAX_XDS_FOR_TR_CALLS of 64 for transmit and
    receive), so even after 4
    
        stty -F /dev/ttyGS0
    
    we cannot transmit anymore.  We can still receive (not necessarily
    reliably) as now we have 16 * 4 = 64 descriptors/buffers ready, but the
    device is otherwise not usable.
    Signed-off-by: NJim Sung <jsung@syncadence.com>
    Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>
    28609d40
u_serial.c 33.7 KB