Hi Dan,
I think this is the same issue one of the patches in type2 support tries
to deal with:
https://lore.kernel.org/linux-cxl/20240907081836.5801-1-alejandro.lucero-palau@xxxxxxx/T/#m9357a559c1a3cc7869ecce44a1801d51518d106e
If this fixes that situation, I guess I can drop that one from v4 which
is ready to be sent.
The other problem I try to fix in that patch, the endpoint not being
there when that code tries to use it, it is likely not needed either,
although I have a trivial fix for it now instead of that ugly loop with
delays. The solution is to add PROBE_FORCE_SYNCHRONOUS as probe_type for
the cxl_mem_driver which implies the device_add will only return when
the device is really created. Maybe that is worth it for other potential
situations suffering the delayed creation.
On 10/11/24 06:33, Dan Williams wrote:
Gregory's modest proposal to fix CXL cxl_mem_probe() failures due to
delayed arrival of the CXL "root" infrastructure [1] prompted questions
of how the existing mechanism for retrying cxl_mem_probe() could be
failing.
The critical missing piece in the debug was that Gregory's setup had
almost all CXL modules built-in to the kernel.
On the way to that discovery several other bugs and init-order corner
cases were discovered.
The main fix is to make sure the drivers/cxl/Makefile object order
supports root CXL ports being fully initialized upon cxl_acpi_probe()
exit. The modular case has some similar potential holes that are fixed
with MODULE_SOFTDEP() and other fix ups. Finally, an attempt to update
cxl_test to reproduce the original report resulted in the discovery of a
separate long standing use after free bug in cxl_region_detach().
[1]: http://lore.kernel.org/20241004212504.1246-1-gourry@xxxxxxxxxx
---
Dan Williams (5):
cxl/port: Fix CXL port initialization order when the subsystem is built-in
cxl/port: Fix cxl_bus_rescan() vs bus_rescan_devices()
cxl/acpi: Ensure ports ready at cxl_acpi_probe() return
cxl/port: Fix use-after-free, permit out-of-order decoder shutdown
cxl/test: Improve init-order fidelity relative to real-world systems
drivers/base/core.c | 35 +++++++
drivers/cxl/Kconfig | 1
drivers/cxl/Makefile | 12 +--
drivers/cxl/acpi.c | 7 +
drivers/cxl/core/hdm.c | 50 +++++++++--
drivers/cxl/core/port.c | 13 ++-
drivers/cxl/core/region.c | 48 +++-------
drivers/cxl/cxl.h | 3 -
include/linux/device.h | 3 +
tools/testing/cxl/test/cxl.c | 200 +++++++++++++++++++++++-------------------
tools/testing/cxl/test/mem.c | 1
11 files changed, 228 insertions(+), 145 deletions(-)
base-commit: 8cf0b93919e13d1e8d4466eb4080a4c4d9d66d7b
