The behavior of RW_*_HELD was updated because it was not quite right.
It is not sufficient to return non-zero when the lock is help, we must
only do this when the current task in the holder.
This means we need to track the lock owner which is not something
tracked in a Linux semaphore. After some experimentation the
solution I settled on was to embed the Linux semaphore at the start
of a larger krwlock_t structure which includes the owner field.
This maintains good performance and allows us to cleanly intergrate
with the kernel lock analysis tools. My reasons:
1) By placing the Linux semaphore at the start of krwlock_t we can
then simply cast krwlock_t to a rw_semaphore and pass that on to
the linux kernel. This allows us to use '#defines so the preprocessor
can do direct replacement of the Solaris primative with the linux
equivilant. This is important because it then maintains the location
information for each rw_* call point.
2) Additionally, by adding the owner to krwlock_t we can keep this
needed extra information adjacent to the lock itself. This removes
the need for a fancy lookup to get the owner which is optimal for
performance. We can also leverage the existing spin lock in the
semaphore to ensure owner is updated correctly.
3) All helper functions which do not need to strictly be implemented
as a define to preserve location information can be done as a static
inline function.
4) Adding the owner to krwlock_t allows us to remove all memory
allocations done during lock initialization. This is good for all
the obvious reasons, we do give up the ability to specific the lock
name. The Linux profiling tools will stringify the lock name used
in the code via the preprocessor and use that.
Update rwlocks validated on:
- SLES10 (ppc64)
- SLES11 (x86_64)
- CHAOS4.2 (x86_64)
- RHEL5.3 (x86_64)
- RHEL6 (x86_64)
- FC11 (x86_64)
It turns out that the previous rwlock implementation worked well but
did not integrate properly with the upstream kernel lock profiling/
analysis tools. This is a major problem since it would be awfully
nice to be able to use the automatic lock checker and profiler.
The problem is that the upstream lock tools use the pre-processor
to create a lock class for each uniquely named locked. Since the
rwsem was embedded in a wrapper structure the name was always the
same. The effect was that we only ended up with one lock class for
the entire SPL which caused the lock dependency checker to flag
nearly everything as a possible deadlock.
The solution was to directly map a krwlock to a Linux rwsem using
a typedef there by eliminating the wrapper structure. This was not
done initially because the rwsem implementation is specific to the arch.
To fully implement the Solaris krwlock API using only the provided rwsem
API is not possible. It can only be done by directly accessing some of
the internal data member of the rwsem structure.
For example, the Linux API provides a different function for dropping
a reader vs writer lock. Whereas the Solaris API uses the same function
and the caller does not pass in what type of lock it is. This means to
properly drop the lock we need to determine if the lock is currently a
reader or writer lock. Then we need to call the proper Linux API function.
Unfortunately, there is no provided API for this so we must extracted this
information directly from arch specific lock implementation. This is
all do able, and what I did, but it does complicate things considerably.
The good news is that in addition to the profiling benefits of this
change. We may see performance improvements due to slightly reduced
overhead when creating rwlocks and manipulating them.
The only function I was forced to sacrafice was rw_owner() because this
information is simply not stored anywhere in the rwsem. Luckily this
appears not to be a commonly used function on Solaris, and it is my
understanding it is mainly used for debugging anyway.
In addition to the core rwlock changes, extensive updates were made to
the rwlock regression tests. Each class of test was extended to provide
more API coverage and to be more rigerous in checking for misbehavior.
This is a pretty significant change and with that in mind I have been
careful to validate it on several platforms before committing. The full
SPLAT regression test suite was run numberous times on all of the following
platforms. This includes various kernels ranging from 2.6.16 to 2.6.29.
- SLES10 (ppc64)
- SLES11 (x86_64)
- CHAOS4.2 (x86_64)
- RHEL5.3 (x86_64)
- RHEL6 (x86_64)
- FC11 (x86_64)
Supported and tested distros now include SLES10, SLES11, Chaos 4.x,
RHEL5, and Fedora 11. This update was mainly to address rebuildable
kernel module rpms, and correct rpm dependencies for each distro.
The run time stack overflow checking is being disabled by default
because it is not safe for use with 2.6.29 and latter kernels. These
kernels do now have their own stack overflow checking so this support
has become redundant anyway. It can be re-enabled for older kernels or
arches without stack overflow checking by redefining CHECK_STACK().
Basically everything we need to monitor the global memory state of
the system is now cleanly available via global_page_state(). The
problem is that this interface is still fairly recent, and there
has been one change in the page state enum which we need to handle.
These changes basically boil down to the following:
- If global_page_state() is available we should use it. Several
autoconf checks have been added to detect the correct enum names.
- If global_page_state() is not available check to see if
get_zone_counts() symbol is available and use that.
- If the get_zone_counts() symbol is not exported we have no choice
be to dynamically aquire it at load time. This is an absolute
last resort for old kernel which we don't want to patch to
cleanly export the symbol.
This interface is going away, and it's not as if most callers actually
use crhold/crfree when working with credentials. So it'll be okay
they we're not taking a reference on the task structure the odds of
it going away while working with a credential and pretty small.
The previous credential implementation simply provided the needed types and
a couple of dummy functions needed. This update correctly ties the basic
Solaris credential API in to one of two Linux kernel APIs.
Prior to 2.6.29 the linux kernel embeded all credentials in the task
structure. For these kernels, we pass around the entire task struct as if
it were the credential, then we use the helper functions to extract the
credential related bits.
As of 2.6.29 a new credential type was added which we can and do fairly
cleanly layer on top of. Once again the helper functions nicely hide
the implementation details from all callers.
Three tests were added to the splat test framework to verify basic
correctness. They should be extended as needed when need credential
functions are added.
Modern kernel build systems at least post 2.6.16 will set this properly
so we should not. In fact post 2.6.28 the include headers have moved
under arch so the guess we make here is completely wrong. Letting
the kernel build system set this ensure it will be correct.
The slab_overcommit test case could hang on a system with fragmented
memory because it was creating a kmem based slab with 256K objects.
To avoid this I've removed the KMC_KMEM flag which allows the slab
to decide if it should be kmem or vmem backed based on the object
side. The slab_lock test shares this code and will also be effected.
But the point of these two tests is to stress cache locking and
memory overcommit, the type of slab is not critical. In fact, allowing
the slab to do the default smart thing is preferable.
Simply pass the ioctl on to the normal handler. If the ioctl
helper macros are used correctly this should be safe as they
will handle the packing/unpacking of the data encoded in the
ioctl command. And actually, if the caller does not use the
IO* macros at all, and just passes small values, it will probably
be OK as well. We only get in to trouble if they try and use
the upper 32-bits. Endianness is not really a concern here, we
we are pretty much assumed they user and kernel will match.
used to scale the number of threads based on the number of online
CPUs. As CPUs are added/removed we should rescale the thread
count appropriately, but currently this is only done at create.
rpms. These should not be fatal because we actually don't need them
until we build the source rpm. When doing mock builds this is
important because these dependent rpms will only be installed if
they are specificed in the source rpms spec file.
- Kernel modules should be built using the LINUX_OBJ Makefiles and
not the LINUX Makefiles to ensure the proper install paths are used.
- Install modules in to addon/spl/
- Ensure no additional kernel module build products are packaged.
- Simplified spl.spec.in which supports RHEL, CHAOS, SLES, FEDORA.
- Allow checking for exported symbols in both Module.symvers
and Module.symvers. My stock SLES kernel ships an objects
directory with Module.symvers, yet produces a Module.symvers
in the local build directory.
- Properly honor --prefix in build system and rpm spec file.
- Add '--define require_kdir' to spec file to support building
rpms against kernel sources installed in non-default locations.
- Add '--define require_kobj' to spec file to support building
rpms against kernel object installed in non-default locations.
- Stop suppressing errors in autogen.sh script.
- Improved logic to detect missing kernel objects when they are
not located with the source. This is the common case for SLES
as well as in-tree chaos kernel builds and is done to simply
support for multiple arches.
- Moved spl-devel build products to /usr/src/spl-<version>, a
spl symlink is created to reference the last installed version.
- Proper ioctl() 32/64-bit binary compatibility. We need to ensure the
ioctl data itself is always packed the same for 32/64-bit binaries.
Additionally, the correct thing to do is encode this size in bytes
as part of the command using _IOC_SIZE().
- Minor formatting changes to respect the 80 character limit.
- Move all SPLAT_SUBSYSTEM_* defines in to splat-ctl.h.
- Increase SPLAT_SUBSYSTEM_UNKNOWN because we were getting close
to accidentally using it for a real registered subsystem.
- Add compat_ioctl() handler, by default 64-bit SLES systems build 32-bit
ELF binaries. For the 32-bit binaries to pass ioctl information to a
64-bit kernel a compatibility handler needs to be registered. In our
case no additional conversions are needed to convert 32-bit ioctl()
commands to 64-bit commands so we can just call the default handler.
- Initial SLES testing uncovered a long standing bug in the debug
tracing. The tcd_for_each() macro expected a NULL to terminate
the trace_data[i] array but this was only ever true due to luck.
All trace_data[] iterators are now properly capped by TCD_TYPE_MAX.
- SPLAT_MAJOR 229 conflicted with a 'hvc' device on my SLES system.
Since this was always an arbitrary choice I picked something else.
- The HAVE_PGDAT_LIST case should set pgdat_list_addr to the value stored
at the address of the memory location returned by kallsyms_lookup_name().
- Prior to 2.6.17 there were no *_pgdat helper functions in mm/mmzone.c.
Instead for_each_zone() operated directly on pgdat_list which may or
may not have been exported depending on how your kernel was compiled.
Now new configure checks determine if you have the helpers or not, and
if the needed symbols are exported. If they are not exported then they
are dynamically aquired at runtime by kallsyms_lookup_name().
- Enable builds for powerpc ISA type.
- Add DIV_ROUND_UP and roundup macros if unavailable.
- Cast 64-bit values for %lld format string to (long long) to
quiet compile warning.
- Configure check for SLES specific API change to vfs_unlink()
and vfs_rename() which added a 'struct vfsmount *' argument.
This was for something called the linux-security-module, but
it appears that it was never adopted upstream.
- Configure check for mutex_lock_nested(). This function was introduced
as part of the mutex validator in 2.6.18, but if it's unavailable then
it's safe to fallback to a plain mutex_lock().
- Configure check, the div64_64() function was renamed to
div64_u64() as of 2.6.26.
- Configure check, the global_page_state() fuction was introduced
in 2.6.18 kernels. The earlier 2.6.16 based SLES10 must not try
and use it, thankfully get_zone_counts() is still available.
- To simplify debugging poison all symbols aquired dynamically
using spl_kallsyms_lookup_name() with SYMBOL_POISON.
- Add console messages when the user mode helpers fail.
- spl_kmem_init_globals() use bit shifts instead of division.
- When the monotonic clock is unavailable __gethrtime() must perform
the HZ division as an 'unsigned long long' because the SPL only
implements __udivdi3(), and not __divdi3() for 'long long' division
on 32-bit arches.
- Exclude -obj when detecting installed kernel source.
- Detect -obj directory for out of tree kernel builds.
- Allow kernel build system to set CC to ensure -m64 is set properly.
This is an issue on 64-bit SLES systems which by default always
build 32-bit binaries (unlike RHEL/Fedora which default to 64-bit)
Brian Behlendorf
Ricardo M. Correia