do not participate in the global symbols namespace, but rtld locks are
still replaced and functions are interposed. In particular,
__pthread_map_stacks_exec is resolved to the libc version. If a
library is loaded later, which requires adjustment of the stack
protection mode, rtld calls into libc __pthread_map_stacks_exec due to
the symbols scope. The libc version might recurse into binder and
recursively acquire rtld bind lock, causing the hang.
Make libc __pthread_map_stacks_exec() interposed, which synchronizes
rtld locks and version of the stack exec hook when libthr loaded,
regardless of the symbol scope control or symbol resolution order.
The __pthread_map_stacks_exec() symbol is removed from the private
version in libthr since libc symbol now operates correctly in presence
of libthr.
Reported and tested by: markj
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
the whole RLIMIT_STACK-sized region of the kernel-allocated stack as
the stack of main thread.
By default, the main thread stack is clamped at 2MB (4MB on 64bit
ABIs) and the rest is used for other threads stack allocation. Since
there is no programmatic way to adjust the size of the main thread
stack, pthread_attr_setstacksize() is too late, the knob allows user
to manage the main stack size both for single-threaded and
multi-threaded processes with the rlimit.
Reported by: "Ivan A. Kosarev" <ivan@ivan-labs.com>
Tested by: dim
Sponsored by: The FreeBSD Foundation
MFC after: 3 days
Stack creation code is changed to call _rtld_get_stack_prot() to get
the stack protection right. There is a race where thread is created
during dlopen() of dso that requires executable stacks. Then,
_rtld_get_stack_prot() may return PROT_READ | PROT_WRITE, but thread
is still not linked into the thread list. In this case, the callback
misses the thread stack, and rechecks the required protection
afterward.
Reviewed by: davidxu
1. fast simple type mutex.
2. __thread tls works.
3. asynchronous cancellation works ( using signal ).
4. thread synchronization is fully based on umtx, mainly, condition
variable and other synchronization objects were rewritten by using
umtx directly. those objects can be shared between processes via
shared memory, it has to change ABI which does not happen yet.
5. default stack size is increased to 1M on 32 bits platform, 2M for
64 bits platform.
As the result, some mysql super-smack benchmarks show performance is
improved massivly.
Okayed by: jeff, mtm, rwatson, scottl
list is protected by a spinlock_t, but the dead list uses a pthread_mutex
because it is necessary to synchronize other threads with the garbage
collector thread. Lock/Unlock macros are used so it's easier to make
changes to the locks in the future.
The 'dead thread list' lock is intended to replace the gc mutex.
This doesn't have any practical ramifications. It simply makes it
clearer what the purpose of the lock is. The gc will use this lock,
instead of the gc mutex, to synchronize access to the dead list with
other threads.
Modify _pthread_exit() to use these two new locks instead of GIANT_LOCK,
and also to properly lock and protect thread state changes,
especially with respect to a joining thread.
The gc thread was also re-arranged to be more organized and less nested.
_pthread_join() was also modified to use the thread list locks. However,
locking and unlocking here needs special care because a thread could find
itself in a position where it's joining an exiting thread that is
waiting on the dead list lock, which this thread (joiner) holds. If the
joiner doesn't take care to lock *and* unlock in the same order they
(the joiner and the joinee) could deadlock against each other.
Approved by: re/blanket libthr
