Some buggy NPTL threading implementations include the guard area within
the stack size allocations. In this case we need to allocate an extra
page to account for the guard area since we only have two pages of usable
stack on Linux. Added an autoconf test that detects such implementations
by running a test program designed to segfault if the bug is present.
Set a flag NPTL_GUARD_WITHIN_STACK that is tested to decide if extra
stack space must be allocated for the guard area.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
There are 3 fixes in thie commit. First, update ztest_run() to store
the thread id and not the address of the kthread_t. This will be freed
on thread exit and is not safe to use. This is pretty close to how
things were done in the original ztest code before I got there.
Second, for extra paranoia update thread_exit() to return a special
TS_MAGIC value via pthread_exit(). This value is then verified in
pthread_join() to ensure the thread exited cleanly. This can be
done cleanly because the kthread doesn't provide a return code
mechanism we need to worry about.
Third, replace the ztest deadman thread with a signal handler. We
cannot use the previous approach because the correct behavior for
pthreads is to wait for all threads to exit before terminating the
process. Since the deadman thread won't call exit by design we
end up hanging in kernel_exit(). To avoid this we just setup a
SIGALRM signal handle and register a deadman alarm. IMHO this
is simpler and cleaner anyway.
There was previous discussion of a race with joinable threads but to
be honest I can neither exactly remember the race, or recrease the
issue. I believe it may have had to do with pthread_create() returning
without having set kt->tid since this was done in the created thread.
If that was the race then I've 'fixed' it by ensuring the thread id
is set in the thread AND as the first pthread_create() argument. Why
this wasn't done originally I'm not sure, with luck Ricardo remembers.
Additionally, explicitly set a PAGESIZE guard frame at the end of the
stack to aid in detecting stack overflow. And add some conditional
logic to set STACK_SIZE correctly for Solaris.
Certain function must never be automatically inlined by gcc because
they are stack heavy or called recursively. This patch flags all
such functions I have found as 'noinline' to prevent gcc from making
the optimization.
This is a portability change which removes the dependence of the Solaris
thread library. All locations where Solaris thread API was used before
have been replaced with equivilant Solaris kernel style thread calls.
In user space the kernel style threading API is implemented in term of
the portable pthreads library. This includes all threads, mutexs,
condition variables, reader/writer locks, and taskqs.
With this patch applied I get the following failure 100% of the time,
I'd prefer to debug it and keep moving forward but I do not have the
time right now so I'm reverting the patch to the version which worked.
Ricardo please fix.
(gdb) bt
0 ztest_dmu_write_parallel (za=0x2aaaac898960) at
../../cmd/ztest/ztest.c:2566
1 0x0000000000405a79 in ztest_thread (arg=<value optimized out>)
at ../../cmd/ztest/ztest.c:3862
2 0x00002b2e6a7a841d in zk_thread_helper (arg=<value optimized out>)
at ../../lib/libzpool/kernel.c:131
3 0x000000379be06367 in start_thread (arg=<value optimized out>)
at pthread_create.c:297
4 0x000000379b2d30ad in clone () from /lib64/libc.so.6
This resolves previous scalabily concerns about the cost of calling
curthread which previously required a list walk. The kthread address
is now tracked as thread specific data which can be quickly returned.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The intent here is to fully remove the previous Solaris thread
implementation so we don't need to simulate both Solaris kernel
and user space thread APIs. The few user space consumers of the
thread API have been updated to use the kthread API. In order
to support this we needed to more fully support the kthread API
and that means not doing crazy things like casting a thread id
to a pointer and using that as was done before. This first
implementation is not effecient but it does provide all the
corrent semantics. If/when performance becomes and issue we
can and should just natively adopt pthreads which is portable.
Let me finish by saying I'm not proud of any of this and I would
love to see it improved. However, this slow implementation does
at least provide all the correct kthread API semantics whereas
the previous method of casting the thread ID to a pointer was
dodgy at best.
code to only use the kthread API regardless of if it is compiled in the
kernel or user space. The kthread API will be layered on top of pthreads
as best as possible in zfs_context, this is non optimal but much clearer.
Brian Behlendorf
Ned Bass
Ricardo M. Correia