Date: Fri, 12 Jul 1996 15:51:58 +0200 (MET DST) From: Nicolas Souchu <Nicolas.Souchu@prism.uvsq.fr> To: freebsd-scsi@freebsd.org Subject: TRY_AGAIN_LATER return value Message-ID: <199607121351.PAA00186@angrand.prism.uvsq.fr>
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>From /sys/scsi/scsi_base.c,
/*
* Do the transfer. If we are polling we will return:
* COMPLETE, Was poll, and scsi_done has been called
* TRY_AGAIN_LATER, Adapter short resources, try again
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
*
* if under full steam (interrupts) it will return:
* SUCCESSFULLY_QUEUED, will do a wakeup when complete
* TRY_AGAIN_LATER, (as for polling)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
*
* After the wakeup, we must still check if it succeeded
*
* If we have a bp however, all the error proccessing
* and the buffer code both expect us to return straight
* to them, so as soon as the command is queued, return
*/
After the last retry, the bp structure is updated like this:
if (bp && retval) {
bp->b_error = retval;
bp->b_flags |= B_ERROR;
biodone(bp);
}
then scsi_scsi_cmd() returns.
Another possibility on short resources is to return HAD_ERROR with
xs->error = XS_BUSY (XS_TIMEOUT is equivalent), then the bp structure
is updated like this in sc_done() after the last retry:
if (bp) {
bp->b_error = 0;
bp->b_flags |= B_ERROR;
bp->b_error = code;
bp->b_resid = bp->b_bcount;
SC_DEBUG(xs->sc_link, SDEV_DB3,
("scsi_interpret_sense (bp) returned %d\n", code));
}
and later...
if (bp && retval) {
bp->b_error = retval;
bp->b_flags |= B_ERROR;
biodone(bp);
}
then scsi_scsi_cmd() returns.
Converting TRY_AGAIN_LATER to HAD_ERROR and XS_BUSY seem to correct
the deadlock bug I previously posted.
What about TRY_AGAIN_LATER then ?
nicolas
--
Nicolas.Souchu@prism.uvsq.fr
Laboratoire PRiSM - Versailles, FRANCE
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