Hi all,
during the debug for the unplug issue reported, I encounter now SIGSEGVs on
other places:
I added some debug output to the libusb/io.c:
int usbi_handle_transfer_completion(struct usbi_transfer *itransfer,
enum libusb_transfer_status status)
{
struct libusb_transfer *transfer =
USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
struct libusb_context *ctx = TRANSFER_CTX(transfer);
struct libusb_device_handle *handle = transfer->dev_handle;
uint8_t flags;
int r = 0;
usbi_dbg("entered... %p",ctx);
/* FIXME: could be more intelligent with the timerfd here. we don't need
* to disarm the timerfd if there was no timer running, and we only need
* to rearm the timerfd if the transfer that expired was the one with
* the shortest timeout. */
usbi_mutex_lock(&ctx->flying_transfers_lock);
usbi_dbg("locked mutex %p %p",itransfer,&itransfer->list);
usbi_dbg("list pointers %p
%p",itransfer->list.next,itransfer->list.prev);
list_del(&itransfer->list);
usbi_dbg("deleted list");
The corresponding output when removing the device is:
[ 6.973000] [00001d59] libusbx: debug [usbi_handle_transfer_completion]
entered... 0x884cdf0
[ 6.973000] [00001d59] libusbx: debug [usbi_handle_transfer_completion] locked
mutex 0x8813eb8 0x8813ebc
[ 6.973000] [00001d59] libusbx: debug [usbi_handle_transfer_completion] list
pointers (nil) (nil)
Caught a signal (11: SIGSEGV)
This can be easily explained because the list_del looks like this:
static inline void list_del(struct list_head *entry)
{
entry->next->prev = entry->prev;
entry->prev->next = entry->next;
entry->next = entry->prev = NULL;
}
=> entry->next and entry->prev are already NULL! So this delete should never be
done, adding some checkings would be helpful.
But when adding a check against NULL for each prev and next in the list_del
before accessing them, the process does not die but stalls on another point when
trying to do a bulk read the device after connecting:
/lib/libusb-1.0.so.0:libusb_ref_device()
/lib/libusb-1.0.so.0:libusb_submit_transfer()
and the last libusb debug output lines are:
[ 6.849000] [00001fae] libusbx: debug [usbi_handle_transfer_completion]
entered... 0x884cdf0
[ 6.849000] [00001fae] libusbx: debug [usbi_handle_transfer_completion] locked
mutex 0x8813eb8 0x8813ebc
[ 6.849000] [00001fae] libusbx: debug [usbi_handle_transfer_completion] list
pointers (nil) (nil)
[ 6.849000] [00001fae] libusbx: debug [usbi_handle_transfer_completion] deleted
list
[ 6.849000] [00001fae] libusbx: debug [usbi_handle_transfer_completion] transfer
0x8813eec has callback 0xb708b0c0
[ 6.849000] [00001fae] libusbx: debug [sync_transfer_cb] actual_length=0
[ 6.849000] [00001fae] libusbx: debug [usbi_handle_transfer_completion] part 3
[ 6.849000] [00001fae] libusbx: debug [usbi_handle_transfer_completion] part 4
[ 6.849000] [00001fae] libusbx: debug [libusb_unref_device] destroy device 2.57
[ 6.849000] [00001fae] libusbx: debug [usbi_handle_transfer_completion] part 5
[ 6.849000] [00001fae] libusbx: debug [op_handle_events] Reap for handle done!
0x884cf40
[ 6.849000] [00001fae] libusbx: debug [op_handle_events] Reap for handle done!
0x884cf40
[ 6.855000] [00001fae] libusbx: debug [submit_bulk_transfer] need 4 urbs for new
transfer with length 65536
[ 6.981000] [00001fa4] libusbx: debug [linux_netlink_read_message] netlink
hotplug found device busnum: 2, devaddr: 57, sys_name: 2-1.4, removed: yes
[ 6.981000] [00001fa4] libusbx: debug [linux_device_disconnected] starting
device disconnect...
[ 6.981000] [00001fa4] libusbx: debug [linux_device_disconnected] lock
acquired...
[ 6.981000] [00001fa4] libusbx: debug [linux_device_disconnected] getting device
by session... 0x884cdf0
[ 6.981000] [00001fa4] libusbx: debug [linux_device_disconnected] device:
0x884f0b8
I don't know exactly how to proceed here - any hint would be appreciated.
Best regards,
Erik
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