- It is opt-out for now so as to give it maximum testing, but it may be
turned opt-in for stable branches depending on the consensus. You
can turn it off with WITHOUT_SSP.
- WITHOUT_SSP was previously used to disable the build of GNU libssp.
It is harmless to steal the knob as SSP symbols have been provided
by libc for a long time, GNU libssp should not have been much used.
- SSP is disabled in a few corners such as system bootstrap programs
(sys/boot), process bootstrap code (rtld, csu) and SSP symbols themselves.
- It should be safe to use -fstack-protector-all to build world, however
libc will be automatically downgraded to -fstack-protector because it
breaks rtld otherwise.
- This option is unavailable on ia64.
Enable GCC stack protection (aka Propolice) for kernel:
- It is opt-out for now so as to give it maximum testing.
- Do not compile your kernel with -fstack-protector-all, it won't work.
Submitted by: Jeremie Le Hen <jeremie@le-hen.org>
locked and unlocked completely in userland. by locking and unlocking mutex
in userland, it reduces the total time a mutex is locked by a thread,
in some application code, a mutex only protects a small piece of code, the
code's execution time is less than a simple system call, if a lock contention
happens, however in current implemenation, the lock holder has to extend its
locking time and enter kernel to unlock it, the change avoids this disadvantage,
it first sets mutex to free state and then enters kernel and wake one waiter
up. This improves performance dramatically in some sysbench mutex tests.
Tested by: kris
Sounds great: jeff
returns errno, because errno can be mucked by user's signal handler and
most of pthread api heavily depends on errno to be correct, this change
should improve stability of the thread library.
_thr_suspend_check() which messes sigmask saved in thread structure.
- Don't suspend a thread has force_exit set.
- In pthread_exit(), if there is a suspension flag set, wake up waiting-
thread after setting PS_DEAD, this causes waiting-thread to break loop
in suspend_common().
that there might be starvations, but because we have already locked the
thread, the cpuset settings will always be done before the new thread
does real-world work.
we set scheduling parameters and cpu binding fully in userland, and
because default scheduling policy is SCHED_RR (time-sharing), we set
default sched_inherit to PTHREAD_SCHED_INHERIT, this saves a system
call.
however if current thread is executing cancellation handler, signal
SIGCANCEL may have already been blocked, this is unexpected, unblock the
signal in new thread if this happens.
MFC after: 1 week
