The pthread_self(), thrd_current() or GetCurrentThreadId() could
actually be a pointer, so we should rather convert the value into
uintptr_t instead of unsigned long.
(cherry picked from commit a0181056a8)
Fix crash on arm64 from using atomic_compare_exchange_weak outside of the loop
See merge request isc-projects/bind9!3042
(cherry picked from commit e4671ef2fa)
fa68a0d8 Added atomic_compare_exchange_strong_acq_rel macro
4cf275ba Replace non-loop usage of atomic_compare_exchange_weak with strong variant
4ff887db Add arm64 to GitLab CI
Start enforcing the clang-format rules on changed files
Closes#46
See merge request isc-projects/bind9!3063
(cherry picked from commit a04cdde45d)
d2b5853b Start enforcing the clang-format rules on changed files
618947c6 Switch AlwaysBreakAfterReturnType from TopLevelDefinitions to All
654927c8 Add separate .clang-format files for headers
5777c44a Reformat using the new rules
60d29f69 Don't enforce copyrights on .clang-format
adjust clang-format options to get closer to ISC style
See merge request isc-projects/bind9!3061
(cherry picked from commit d3b49b6675)
0255a974 revise .clang-format and add a C formatting script in util
e851ed0b apply the modified style
Add curly braces using uncrustify and then reformat with clang-format back
Closes#46
See merge request isc-projects/bind9!3057
(cherry picked from commit 67b68e06ad)
36c6105e Use coccinelle to add braces to nested single line statement
d14bb713 Add copy of run-clang-tidy that can fixup the filepaths
056e133c Use clang-tidy to add curly braces around one-line statements
Reformat source code with clang-format
Closes#46
See merge request isc-projects/bind9!2156
(cherry picked from commit 7099e79a9b)
4c3b063e Import Linux kernel .clang-format with small modifications
f50b1e06 Use clang-format to reformat the source files
11341c76 Update the definition files for Windows
df6c1f76 Remove tkey_test (which is no-op anyway)
The memory ordering in the rwlock was all wrong, I am copying excerpts
from the https://en.cppreference.com/w/c/atomic/memory_order#Relaxed_ordering
for the convenience of the reader:
Relaxed ordering
Atomic operations tagged memory_order_relaxed are not synchronization
operations; they do not impose an order among concurrent memory
accesses. They only guarantee atomicity and modification order
consistency.
Release-Acquire ordering
If an atomic store in thread A is tagged memory_order_release and an
atomic load in thread B from the same variable is tagged
memory_order_acquire, all memory writes (non-atomic and relaxed atomic)
that happened-before the atomic store from the point of view of thread
A, become visible side-effects in thread B. That is, once the atomic
load is completed, thread B is guaranteed to see everything thread A
wrote to memory.
The synchronization is established only between the threads releasing
and acquiring the same atomic variable. Other threads can see different
order of memory accesses than either or both of the synchronized
threads.
Which basically means that we had no or weak synchronization between
threads using the same variables in the rwlock structure. There should
not be a significant performance drop because the critical sections were
already protected by:
while(1) {
if (relaxed_atomic_operation) {
break;
}
LOCK(lock);
if (!relaxed_atomic_operation) {
WAIT(sem, lock);
}
UNLOCK(lock)l
}
I would add one more thing to "Don't do your own crypto, folks.":
- Also don't do your own locking, folks.
The change fixes the following build failure on sparc T3 and older CPUs:
```
sparc-unknown-linux-gnu-gcc ... -O2 -mcpu=niagara2 ... -c rwlock.c
{standard input}: Assembler messages:
{standard input}:398: Error: Architecture mismatch on "pause ".
{standard input}:398: (Requires v9e|v9v|v9m|m8; requested architecture is v9b.)
make[1]: *** [Makefile:280: rwlock.o] Error 1
```
`pause` insutruction exists only on `-mcpu=niagara4` (`T4`) and upper.
The change adds `pause` configure-time autodetection and uses it if available.
config.h.in got new `HAVE_SPARC_PAUSE` knob. Fallback is a fall-through no-op.
Build-tested on:
- sparc-unknown-linux-gnu-gcc (no `pause`, build succeeds)
- sparc-unknown-linux-gnu-gcc -mcpu=niagara4 (`pause`, build succeeds)
Reported-by: Rolf Eike Beer
Bug: https://bugs.gentoo.org/691708
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
The ThreadSanitizer found several possible data races in our rwlock
implementation. This commit changes all the unprotected variables to atomic and
also changes the explicit memory ordering (atomic_<foo>_explicit(..., <order>)
functions to use our convenience macros (atomic_<foo>_<order>).
The stock toolchain available on CentOS 6 for i386 is unable to use the
_mm_pause() intrinsic. Fix by using "rep; nop" assembly instructions on
that platform instead.
