Merge #12923: util: Pass pthread_self() to pthread_setschedparam inst…

…ead of 0

Summary:
b86730a util: Remove designator initializer from ScheduleBatchPriority (Wladimir J. van der Laan)
cff66e6 util: Pass pthread_self() to pthread_setschedparam instead of 0 (Wladimir J. van der Laan)

Pull request description:

  Nowhere in the man page of `pthread_setschedparam` it is mentioned that `0` is a valid value. The example uses `pthread_self()`, so should we.

  (noticed by Anthony Towns)
  Fixes #12915.

Tree-SHA512: 249e93b1ae7e3ba28de6ee6288400b91d21ca1b4ca41d82211f6c9609b62deb5ac87182c7bf08471d3a3e0c1af314c9ecd41f8ae864febe963b1de8a816dd82f

Backport of Core PR12923
bitcoin/bitcoin#12923

Depends on D3953

Test Plan:
  make check
  test_runner.py

Reviewers: deadalnix, Fabien, jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Reviewed By: deadalnix, O1 Bitcoin ABC, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D3954

src/util.cpp

@@ -1315,8 +1315,8 @@ fs::path AbsPathForConfigVal(const fs::path &path, bool net_specific) {
 
 int ScheduleBatchPriority() {
 #ifdef SCHED_BATCH
-    const static sched_param param{.sched_priority = 0};
-    if (int ret = pthread_setschedparam(0, SCHED_BATCH, &param)) {
+    const static sched_param param{0};
+    if (int ret = pthread_setschedparam(pthread_self(), SCHED_BATCH, &param)) {
         LogPrintf("Failed to pthread_setschedparam: %s\n", strerror(errno));
         return ret;
     }