Add infrastructure so that periphs can use sbufs for device
arrival announcements. Only scsi_da is converted at the moment,
everything else remains working and unchanged. Have not added
device departure infrastructure, nor ATA/SATA infrastructure.
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So, the question is, should we just have one version of these functions, and use a stack buffer to re-implement in terms of the new sbuf routines, or would we risk stack overflow?
| sys/cam/cam_xpt.c | ||
|---|---|---|
| 1079 | Instead of duplicating xpt_announce_periph() in sbuf form, what do you think about re-implementing it to just call xpt_announce_periph_sbuf() with a static buffer and then printf that? I guess the question would be how big of a stack buffer we're talking about, and whether that would cause things to blow up in any particular situation. | |
| 1144 | Same question here. | |
| sys/cam/scsi/scsi_all.c | ||
| 5476 | And I suppose the same question goes here. Should we just implement scsi_print_inquiry() in terms of scsi_print_inquiry_sbuf()? | |
| sys/cam/scsi/scsi_xpt.c | ||
| 3132 | And the same question here. Should we just re-implement in terms of scsi_announce_periph_sbuf()? | |
| sys/cam/cam_xpt.c | ||
|---|---|---|
| 1079 | This path has had problems in the past with blowing out the stack. Adding more to the stack makes me nervous. We can try your suggestion, and I've done it to a lesser degree in some places. However what I'd really like to do is get everything converted, add fine-grained draining, and then remove the legacy functions. This is just an intermediate step to that goal. | |
| sys/cam/scsi/scsi_all.c | ||
|---|---|---|
| 5476 | Would there be any side effects in camcontrol and other userland utilities from doing this? I would have to be careful about using sbuf_putbuf() because it doesn't exist in userland (and I'm not sure how it would be implemented there). | |
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This has already landed.
commit 5d01277f596ee9b05b6b19b6a55fe84668ffc100 Author: Scott Long <scottl@FreeBSD.org> Date: Wed Apr 19 15:04:52 2017 +0000 Add infrastructure to the ATA and SCSI transports that supports using a driver-supplied sbuf for printing device discovery announcements. This helps ensure that messages to the console will be properly serialized (through sbuf_putbuf) and not be truncated and interleaved with other messages. The infrastructure mirrors the existing xpt_announce_periph() entry point and is opt-in for now. No content or formatting changes are visible to the operator other than the new coherency. While here, eliminate the stack usage of the temporary announcement buffer in some of the drivers. It's moved to the softc for now, but future work will eliminate it entirely by making the code flow more linear. Future work will also address locking so that the sbufs can be dynamically sized. The scsi_da, scs_cd, scsi_ses, and ata_da drivers are converted at this point, other drivers can be converted at a later date. A tunable+sysctl, kern.cam.announce_nosbuf, exists for testing purposes but will be removed later. TODO: Eliminate all of the code duplication and temporary buffers. The old printf-based methods will be retired, and xpt_announce_periph() will just be a wrapper that uses a dynamically sized sbuf. This requires that the register and deregister paths be made malloc-safe, which they aren't currently. Sponsored by: Netflix Notes: svn path=/head/; revision=317143