svn commit: r357698 - head/lib/libthr/thread

[Konstantin Belousov]

Author: kib
Date: Sun Feb  9 12:27:22 2020
New Revision: 357698
URL: https://svnweb.freebsd.org/changeset/base/357698

Log:
  Use sigfastblock(2) for masking signals in libthr.
  
  Ensure proper handshake to transfer sigfastblock(2) blocking word
  ownership from rtld to libthr.
  
  Unfortunately sigfastblock(2) is not enough to stop intercepting
  signals in libthr, because critical sections must ensure more than
  just signal blocking.
  
  Tested by:	pho
  Disscussed with:	cem, emaste, jilles
  Sponsored by:	The FreeBSD Foundation
  Differential revision:	https://reviews.freebsd.org/D12773

Modified:
  head/lib/libthr/thread/thr_create.c
  head/lib/libthr/thread/thr_private.h
  head/lib/libthr/thread/thr_rtld.c
  head/lib/libthr/thread/thr_sig.c

Modified: head/lib/libthr/thread/thr_create.c
==============================================================================
--- head/lib/libthr/thread/thr_create.c	Sun Feb  9 12:22:43 2020	(r357697)
+++ head/lib/libthr/thread/thr_create.c	Sun Feb  9 12:27:22 2020	(r357698)
@@ -257,6 +257,7 @@ thread_start(struct pthread *curthread)
 
 	if (curthread->attr.suspend == THR_CREATE_SUSPENDED)
 		set = curthread->sigmask;
+	_thr_signal_block_setup(curthread);
 
 	/*
 	 * This is used as a serialization point to allow parent

Modified: head/lib/libthr/thread/thr_private.h
==============================================================================
--- head/lib/libthr/thread/thr_private.h	Sun Feb  9 12:22:43 2020	(r357697)
+++ head/lib/libthr/thread/thr_private.h	Sun Feb  9 12:27:22 2020	(r357698)
@@ -396,6 +396,9 @@ struct pthread {
 	/* Signal blocked counter. */
 	int			sigblock;
 
+	/* Fast sigblock var. */
+	uint32_t		fsigblock;
+
 	/* Queue entry for list of all threads. */
 	TAILQ_ENTRY(pthread)	tle;	/* link for all threads in process */
 
@@ -813,6 +816,8 @@ void	_thr_cancel_leave(struct pthread *, int) __hidden
 void	_thr_testcancel(struct pthread *) __hidden;
 void	_thr_signal_block(struct pthread *) __hidden;
 void	_thr_signal_unblock(struct pthread *) __hidden;
+void	_thr_signal_block_check_fast(void) __hidden;
+void	_thr_signal_block_setup(struct pthread *) __hidden;
 void	_thr_signal_init(int) __hidden;
 void	_thr_signal_deinit(void) __hidden;
 int	_thr_send_sig(struct pthread *, int sig) __hidden;

Modified: head/lib/libthr/thread/thr_rtld.c
==============================================================================
--- head/lib/libthr/thread/thr_rtld.c	Sun Feb  9 12:22:43 2020	(r357697)
+++ head/lib/libthr/thread/thr_rtld.c	Sun Feb  9 12:27:22 2020	(r357698)
@@ -236,6 +236,8 @@ _thr_rtld_init(void)
 	_thr_signal_block(curthread);
 	_rtld_thread_init(&li);
 	_thr_signal_unblock(curthread);
+	_thr_signal_block_check_fast();
+	_thr_signal_block_setup(curthread);
 
 	uc_len = __getcontextx_size();
 	uc = alloca(uc_len);

Modified: head/lib/libthr/thread/thr_sig.c
==============================================================================
--- head/lib/libthr/thread/thr_sig.c	Sun Feb  9 12:22:43 2020	(r357697)
+++ head/lib/libthr/thread/thr_sig.c	Sun Feb  9 12:27:22 2020	(r357698)
@@ -31,7 +31,8 @@ __FBSDID("$FreeBSD$");
 
 #include "namespace.h"
 #include <sys/param.h>
-#include <sys/types.h>
+#include <sys/auxv.h>
+#include <sys/elf.h>
 #include <sys/signalvar.h>
 #include <sys/syscall.h>
 #include <signal.h>
@@ -92,10 +93,9 @@ static const sigset_t _thr_maskset={{
 	0xffffffff,
 	0xffffffff}};
 
-void
-_thr_signal_block(struct pthread *curthread)
+static void
+thr_signal_block_slow(struct pthread *curthread)
 {
-	
 	if (curthread->sigblock > 0) {
 		curthread->sigblock++;
 		return;
@@ -104,11 +104,66 @@ _thr_signal_block(struct pthread *curthread)
 	curthread->sigblock++;
 }
 
-void
-_thr_signal_unblock(struct pthread *curthread)
+static void
+thr_signal_unblock_slow(struct pthread *curthread)
 {
 	if (--curthread->sigblock == 0)
 		__sys_sigprocmask(SIG_SETMASK, &curthread->sigmask, NULL);
+}
+
+static void
+thr_signal_block_fast(struct pthread *curthread)
+{
+	atomic_add_32(&curthread->fsigblock, SIGFASTBLOCK_INC);
+}
+
+static void
+thr_signal_unblock_fast(struct pthread *curthread)
+{
+	uint32_t oldval;
+
+	oldval = atomic_fetchadd_32(&curthread->fsigblock, -SIGFASTBLOCK_INC);
+	if (oldval == (SIGFASTBLOCK_PEND | SIGFASTBLOCK_INC))
+		__sys_sigfastblock(SIGFASTBLOCK_UNBLOCK, NULL);
+}
+
+static bool fast_sigblock;
+
+void
+_thr_signal_block(struct pthread *curthread)
+{
+	if (fast_sigblock)
+		thr_signal_block_fast(curthread);
+	else
+		thr_signal_block_slow(curthread);
+}
+
+void
+_thr_signal_unblock(struct pthread *curthread)
+{
+	if (fast_sigblock)
+		thr_signal_unblock_fast(curthread);
+	else
+		thr_signal_unblock_slow(curthread);
+}
+
+void
+_thr_signal_block_check_fast(void)
+{
+	int bsdflags, error;
+
+	error = elf_aux_info(AT_BSDFLAGS, &bsdflags, sizeof(bsdflags));
+	if (error != 0)
+		return;
+	fast_sigblock = (bsdflags & ELF_BSDF_SIGFASTBLK) != 0;
+}
+
+void
+_thr_signal_block_setup(struct pthread *curthread)
+{
+	if (!fast_sigblock)
+		return;
+	__sys_sigfastblock(SIGFASTBLOCK_SETPTR, &curthread->fsigblock);
 }
 
 int