From 33c8b02fd8ae4e20728d11cbf06a9e18d546af6b Mon Sep 17 00:00:00 2001 From: mtm Date: Sun, 25 May 2003 07:58:22 +0000 Subject: The libthr code makes use of higher-level primitives (pthread_mutex_t and pthread_cond_t) internaly in addition to the low-level spinlock_t. The garbage collector mutex and condition variable are two such examples. This might lead to critical sections nested within critical sections. Implement a reference counting mechanism so that signals are masked only on the first entry and unmasked on the last exit. I'm not sure I like the idea of nested critical sections, but if the library is going to use the pthread primitives it might be necessary. Approved by: re/blanket libthr --- lib/libthr/thread/thr_kern.c | 13 +++++++++++++ lib/libthr/thread/thr_private.h | 1 + 2 files changed, 14 insertions(+) (limited to 'lib/libthr') diff --git a/lib/libthr/thread/thr_kern.c b/lib/libthr/thread/thr_kern.c index 77b0094..1c9a8ce 100644 --- a/lib/libthr/thread/thr_kern.c +++ b/lib/libthr/thread/thr_kern.c @@ -68,6 +68,13 @@ _thread_critical_enter(pthread_t pthread) * acquired the giant lock. */ _SPINLOCK(&pthread->lock); + + /* If we are already in a critical section, just up the refcount */ + if (++curthread->crit_ref > 1) + return; + PTHREAD_ASSERT(curthread->crit_ref == 1, + ("Critical section reference count must be 1!")); + if (__sys_sigprocmask(SIG_SETMASK, &set, &sav)) { _thread_printf(STDERR_FILENO, "Critical Enter: sig err %d\n", errno); @@ -81,6 +88,12 @@ _thread_critical_exit(pthread_t pthread) { sigset_t set; + /* We might be in a nested critical section */ + if (--curthread->crit_ref > 0) + return; + PTHREAD_ASSERT(curthread->crit_ref == 0, + ("Non-Zero critical section reference count.")); + /* * Restore signals. */ diff --git a/lib/libthr/thread/thr_private.h b/lib/libthr/thread/thr_private.h index b02df32..6048bd0 100644 --- a/lib/libthr/thread/thr_private.h +++ b/lib/libthr/thread/thr_private.h @@ -426,6 +426,7 @@ struct pthread { u_int64_t uniqueid; /* for gdb */ thr_id_t thr_id; sigset_t savedsig; + int crit_ref; /* crit. section netsting level */ /* * Lock for accesses to this thread structure. -- cgit v1.1