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thread_pthread.c: document sigwait_th and sigwait_fd [ci skip]

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This is an important concept to document, I think.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64580 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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normal 2018-08-27 23:39:58 +00:00
parent 1b1274f728
commit fcaf874585
1 changed files with 8 additions and 1 deletions
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9
thread_pthread.c
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@ -134,6 +134,13 @@ static void threadptr_trap_interrupt(rb_thread_t *);
/* for testing, and in case we come across a platform w/o pipes: */
#define BUSY_WAIT_SIGNALS (0)
/*
* sigwait_th is the thread which owns sigwait_fd and sleeps on it
* (using ppoll). MJIT worker can be sigwait_th==0, so we initialize
* it to THREAD_INVALID at startup and fork time. It is the ONLY thread
* allowed to read from sigwait_fd, otherwise starvation can occur.
*/
#define THREAD_INVALID ((const rb_thread_t *)-1)
static const rb_thread_t *sigwait_th;
@ -1380,7 +1387,7 @@ static int ubf_threads_empty(void) { return 1; }
static struct {
/* pipes are closed in forked children when owner_process does not match */
int normal[2];
int normal[2]; /* [0] == sigwait_fd */
/* volatile for signal handler use: */
volatile rb_pid_t owner_process;