Implement queueing of threads before dispatching them

It is possible that some tracees call a lot of cheap syscalls too fast,
and that can lead to starvation to the point some tracees are not served
for indefinite amount of time.  In order to solve that unfairness, try
to collect all the pending tracees first along with the relevant
information and only then dispatch the events.

* defs.h: Include "list.h".
(struct tcb): Add wait_data_idx and wait_list fields.
* strace.c (struct tcb_wait_data): Add "msg" field.
(tcb_wait_tab): New static variable.
(expand_tcbtab): Resize tcb_wait_tab along with tcbtab, provide
an additional slot for extra event.
(droptcb): Remove tcp from wait_list.
(maybe_switch_tcbs): Get old pid from
tcb_wait_tab[tcp->wait_data_idx].msg.
(next_event): Add pending_tcps, extra_tcp, wait_nohang, elem, and
wait_tab_pos variables; check for elements in pending_tcps and skip
waiting if the list is not empty; check for extra_tcp and skip waiting
along with swapping wait_data_idx with wait_extra_data_idx;
after the initial wait, call wait4() in loop with WNOHANG flag set;
fetch siginfo on signal and eventmsg on PTRACE_EVENT_EXEC;
return the first tcp in pending_tcps list.
* tests/Makefile.am (XFAIL_TEST): Remove looping_threads.test.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=478419
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=526740
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=851457
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1609318
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1610774
Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org>
Co-Authored-by: Denys Vlasenko <dvlasenk@redhat.com>
Co-Authored-by: Andreas Schwab <aschwab@redhat.com>
Co-Authored-by: Jeff Law <law@redhat.com>
Co-Authored-by: DJ Delorie <dj@redhat.com>

.gitignore

@@ -25,6 +25,7 @@
 /configure
 /depcomp
 /gnu
+/INSTALL
 /install-sh
 /ioctl_iocdef.[ih]
 /ioctl_redefs[12].h

INSTALL-git.md

@@ -5,5 +5,5 @@ that are needed to build strace.  Some of these files are generated by tools
 from the GNU Autoconf and GNU Automake packages.
 
 Note: rather than running `autoreconf` directly, please invoke `./bootstrap`
-script and follow the instructions given in [INSTALL](INSTALL) file for further
+script and follow the instructions given in [INSTALL](README-configure) file for further
 building and installation.

Makefile.am

@@ -185,6 +185,7 @@ strace_SOURCES =	\
 	linux/asm_stat.h \
 	linux/x32/asm_stat.h \
 	linux/x86_64/asm_stat.h \
+	list.h		\
 	listen.c	\
 	lookup_dcookie.c \
 	loop.c		\
@@ -267,6 +268,7 @@ strace_SOURCES =	\
 	ptp.c		\
 	ptrace.h	\
 	quota.c		\
+	random_ioctl.c	\
 	readahead.c	\
 	readlink.c	\
 	reboot.c	\
@@ -402,6 +404,7 @@ EXTRA_DIST =				\
 	CREDITS				\
 	ChangeLog			\
 	ChangeLog-CVS			\
+	README-configure		\
 	README-linux-ptrace		\
 	debian/changelog		\
 	debian/compat			\

NEWS

@@ -1,3 +1,6 @@
+Noteworthy changes in release ?.?? (????-??-??)
+===============================================
+
 Noteworthy changes in release 4.25 (2018-10-30)
 ===============================================
 

README-configure

@@ -15,10 +15,10 @@ Basic Installation
 Briefly, the shell command './configure && make && make install' should
 configure, build, and install this package.  The following more-detailed
 instructions are generic; see the 'README' file for instructions
-specific to this package.  Some packages provide this 'INSTALL' file but
-do not implement all of the features documented below.  The lack of an
-optional feature in a given package is not necessarily a bug.  More
-recommendations for GNU packages can be found in *note Makefile
+specific to this package.  Some packages provide this 'README-configure'
+file but do not implement all of the features documented below.  The
+lack of an optional feature in a given package is not necessarily a bug.
+More recommendations for GNU packages can be found in *note Makefile
 Conventions: (standards)Makefile Conventions.
 
    The 'configure' shell script attempts to guess correct values for

README.md

@@ -9,6 +9,8 @@ See the file [NEWS](NEWS) for information on what has changed in recent versions
 
 Please read the file [INSTALL-git](INSTALL-git.md) for installation instructions.
 
+Please take a look at [the guide for new contributors](https://strace.io/wiki/NewContributorGuide) if you want to get involved in strace development.
+
 The user discussion and development of strace take place on [the strace mailing list](https://lists.strace.io/mailman/listinfo/strace-devel) -- everyone is welcome to post bug reports, feature requests, comments and patches to strace-devel@lists.strace.io.  The mailing list archives are available at https://lists.strace.io/pipermail/strace-devel/ and other archival sites.
 
 The GIT repository of strace is available at [GitHub](https://github.com/strace/strace/) and [GitLab](https://gitlab.com/strace/strace/).

bootstrap

@@ -26,7 +26,7 @@ for m in m32 mx32; do
 	done
 done
 
-for f in README; do
+for f in README INSTALL; do
 	cp "dist/$f" .
 done
 

debian/changelog.in

@@ -4,6 +4,12 @@ strace (@PACKAGE_VERSION@-1) experimental; urgency=low
 
  -- Strace <@PACKAGE_BUGREPORT@>  @DEB_CHANGELOGTIME@
 
+strace (4.25-1) unstable; urgency=medium
+
+  * New upstream version.
+
+ -- Dmitry V. Levin <ldv@altlinux.org>  Tue, 30 Oct 2018 08:09:10 +0000
+
 strace (4.24-1) unstable; urgency=medium
 
   * New upstream version.

defs.h

@@ -57,6 +57,7 @@
 #include "error_prints.h"
 #include "gcc_compat.h"
 #include "kernel_types.h"
+#include "list.h"
 #include "macros.h"
 #include "mpers_type.h"
 #include "string_to_uint.h"
@@ -236,6 +237,15 @@ struct tcb {
 
 	struct mmap_cache_t *mmap_cache;
 
+	/*
+	 * Data that is stored during process wait traversal.
+	 * We use indices as the actual data is stored in an array
+	 * that is realloc'ed in runtime.
+	 */
+	size_t wait_data_idx;
+	struct list_item wait_list;
+
+
 #ifdef HAVE_LINUX_KVM_H
 	struct vcpu_info *vcpu_info_list;
 #endif
@@ -973,6 +983,7 @@ DECL_IOCTL(kvm);
 DECL_IOCTL(nbd);
 DECL_IOCTL(nsfs);
 DECL_IOCTL(ptp);
+DECL_IOCTL(random);
 DECL_IOCTL(scsi);
 DECL_IOCTL(term);
 DECL_IOCTL(ubi);

dist/INSTALL

@@ -0,0 +1,134 @@
+0. BUILD REQUIREMENTS
+
+ - Sane POSIX shell.
+ - gcc-like compiler that supports C99 and some GNU extensions (namely, empty
+   structures, empty definitions, zero length arrays, ranged designated
+   initialisers).
+ - libc. GNU libc and musl are supported.
+ - Linux UAPI headers.
+ - GNU Make.
+ - GNU coreutils.
+ - For running test suite: gawk, grep, sed, runtime environment for all
+   personalities.
+ - Requirements for optional features are documented in their description.
+
+1. CONFIGURATION AND OPTIONAL FEATURES
+
+Configuration is done using GNU Autoconf-generated configure script.
+Please refer to the README-configure file for generic information regarding
+configure usage.
+
+In addition to standard configure options, strace's configure file provides
+the following options:
+
+1.1. Additional build and testing hardening
+
+  --enable-gcc-Werror     turn on gcc's -Werror option
+  --enable-code-coverage  Whether to enable code coverage support
+  --with-gcov=GCOV        use given GCOV for coverage (GCOV=gcov).
+  --enable-valgrind       Whether to enable Valgrind on the unit tests
+  --disable-valgrind-memcheck
+                          Whether to skip memcheck during the Valgrind tests
+  --disable-valgrind-helgrind
+                          Whether to skip helgrind during the Valgrind tests
+  --disable-valgrind-drd  Whether to skip drd during the Valgrind tests
+  --enable-valgrind-sgcheck
+                          Whether to use sgcheck during the Valgrind tests
+
+1.2. Optional features
+
+1.2.1. Multiple personalities support
+
+  --enable-mpers=yes|no|check|m32|mx32
+                          whether to enable multiple personalities support
+                          required for proper decoding of structures used by
+                          tracees with personalities that differ from the
+                          personality of strace, default is yes.
+
+Personality is a way system call is performed (in terms of ABI). For example,
+Linux kernel on multiple 64-bit architectures that evolve from their 32-bit
+counterparts have support for running 32-bit binaries with 32-bit system call
+ABI, and that system call ABI constitutes a separate personality in strace's
+terms. Another example is 32-on-64 bit ABI; while exploiting the same way for
+performing system calls as native 64-bit system calls, this ABI has different
+type sizes and, as a result, also constitutes a separate personality; the only
+such ABI that is currently supported by strace is x32 on x86_64. This is
+important as different ABIs use different alignments and type sizes, as a
+result, fields in structures in unions have different offsets on different
+ABIs. In order to be able to correctly parse all the structures used in various
+system calls and ioctl commands, strace compiles these structure definitions
+for these different ABI and then parses DWARF of these compiled definitions in
+order to generate proper structure definitions that compiled with decoder code.
+Taking the aforementioned into account, there are the following requirements:
+
+ - gawk (at least version 3)
+ - Ability to compile for m32 personality (on architectures where it is supported)
+  - On x86_64, x32, powerpc64, sparc64, riscv64, tile64: gcc -m32
+  - s390x: gcc -m31
+  - AArch64: a separate compiler for armv7 EABI
+   - See information about configuration in "1.3.2. AArch64: AArch32 support"
+ - Ability to compile for mx32 personality (on architectures where it is supported)
+  - On x86_64: gcc -mx32
+ - For tests: runtime support (linker, libc, and loader)
+
+1.2.2. Stack unwinding (-k option)
+
+  --with-libunwind        use libunwind to implement stack tracing support
+  --with-libiberty        use libiberty to demangle symbols in stack trace
+
+1.3. Architecture-specific features
+
+1.3.1. ARMv7: OABI support
+
+  --enable-arm-oabi       enable OABI support on ARM EABI
+
+1.3.2. AArch64: AArch32 support
+
+  CC_FOR_M32
+  CPP_FOR_M32
+  CFLAGS_FOR_M32
+  CPPFLAGS_FOR_M32
+
+1.4. Miscellanea
+
+1.4.1. Static build configuration
+
+For static linking, provide LDFLAGS='-static -pthread'.
+
+1.4.2. Cross-compilation configuration
+
+2. BUILDING
+
+make
+make V=1
+
+3. TESTING
+
+make check
+
+TESTS='list of tests'
+VALGRIND_FLAGS
+TIMEOUT_DURATION
+
+BTRFS_MOUNTPOINT
+
+4. ADDITIONAL TARGETS
+
+  make code-coverage-capture
+  make code-coverage-capture CODE_COVERAGE_BRANCH_COVERAGE=
+
+5. INSTALLATION
+
+make install
+
+6. PACKAGING
+
+6.1. Distribution tarball
+
+./make-dist
+
+Requires git
+
+6.2. dpkg package
+
+6.3. RPM package

dist/README

@@ -10,13 +10,21 @@ of Paul Kranenburg; see the file COPYING for details.
 See the file CREDITS for a list of authors and other contributors.
 See the file INSTALL for compilation and installation instructions.
 See the file NEWS for information on what has changed in recent versions.
+See the file README-hacking for information related to strace development.
 
 The project's homepage is at
 	https://strace.io
 
+The GIT repository of strace is available at
+	https://github.com/strace/strace/ and https://gitlab.com/strace/strace/
+
 strace has a mailing list:
 	strace-devel@lists.strace.io
 
+Everyone is welcome to post bug reports, feature requests, comments
+and patches to the list.  The mailing list archives are available at
+	https://lists.strace.io/pipermail/strace-devel/
+
 System requirements:
 	* Linux kernel >= 2.6.18 is recommended.  Older versions might still work
 	  but they haven't been thoroughly tested with this release.

ioctl.c

@@ -329,6 +329,8 @@ ioctl_decode(struct tcb *tcp)
 		return inotify_ioctl(tcp, code, arg);
 	case 0xab:
 		return nbd_ioctl(tcp, code, arg);
+	case 'R':
+		return random_ioctl(tcp, code, arg);
 	default:
 		break;
 	}

list.h

@@ -0,0 +1,137 @@
+/*
+ * Some simple implementation of a list similar to one used in the kernel.
+ *
+ * Copyright (c) 2016-2018 The strace developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef STRACE_LIST_H
+#define STRACE_LIST_H
+
+#include "macros.h"
+
+struct list_item {
+	struct list_item *prev;
+	struct list_item *next;
+};
+
+#define EMPTY_LIST(l_) struct list_item l_ = { &l_, &l_ }
+
+static inline void
+list_init(struct list_item *l)
+{
+	l->prev = l;
+	l->next = l;
+}
+
+static inline bool
+list_is_empty(struct list_item *l)
+{
+	return (l->next == l) && (l->prev == l);
+}
+
+#define list_elem(var, type, field) containerof((var), type, field)
+
+#define list_head(head, type, field) \
+	(list_is_empty(head) ? NULL : list_elem((head)->next, type, field))
+#define list_tail(head, type, field) \
+	(list_is_empty(head) ? NULL : list_elem((head)->prev, type, field))
+
+#define list_next(val, field) \
+	list_elem((val)->field.next, typeof(*(val)), field)
+#define list_prev(val, field) \
+	list_elem((val)->field.prev, typeof(*(val)), field)
+
+static inline void
+list_insert(struct list_item *head, struct list_item *item)
+{
+	item->next = head->next;
+	item->prev = head;
+	head->next->prev = item;
+	head->next = item;
+}
+
+static inline void
+list_append(struct list_item *head, struct list_item *item)
+{
+	item->next = head;
+	item->prev = head->prev;
+	head->prev->next = item;
+	head->prev = item;
+}
+
+static inline void
+list_remove(struct list_item *item)
+{
+	if (!item->next || !item->prev)
+		return;
+
+	item->prev->next = item->next;
+	item->next->prev = item->prev;
+	item->next = item->prev = NULL;
+}
+
+static inline struct list_item *
+list_remove_tail(struct list_item *head)
+{
+	struct list_item *t = list_is_empty(head) ? NULL : head->prev;
+
+	if (t)
+		list_remove(t);
+
+	return t;
+}
+
+static inline struct list_item *
+list_remove_head(struct list_item *head)
+{
+	struct list_item *h = list_is_empty(head) ? NULL : head->next;
+
+	if (h)
+		list_remove(h);
+
+	return h;
+}
+
+static inline void
+list_replace(struct list_item *old, struct list_item *new)
+{
+	new->next = old->next;
+	new->prev = old->prev;
+	old->prev->next = new;
+	old->next->prev = new;
+	old->next = old->prev = NULL;
+}
+
+#define list_foreach(var_, head_, field_) \
+	for (var_ = list_elem((head_)->next, typeof(*var_), field_); \
+	    &(var_->field_) != (head_); var_ = list_next(var_, field_))
+
+#define list_foreach_safe(var_, head_, field_, _tmp) \
+	for (var_ = list_elem((head_)->next, typeof(*var_), field_), \
+	    _tmp = list_elem((var_)->field_.next, typeof(*var_), field_); \
+	    &var_->field_ != head_; var_ = _tmp, _tmp = list_next(_tmp, field_))
+
+#endif /* !STRACE_LIST_H */

macros.h

@@ -57,6 +57,15 @@
 	(offsetof(type_, member_) + sizeof(((type_ *)0)->member_))
 #endif
 
+#ifndef cast_ptr
+# define cast_ptr(type, var) ((type) (uintptr_t) (const volatile void *) (var))
+#endif
+
+#ifndef containerof
+# define containerof(x, s, m)	\
+	cast_ptr(s *, (const volatile char *) (x) - offsetof(s, m))
+#endif
+
 static inline bool
 is_filled(const char *ptr, char fill, size_t size)
 {

maint/install.texi

@@ -1,5 +1,5 @@
 @c This file is imported from GNU Autoconf and edited to produce
-@c the INSTALL file.
+@c the README-configure file.
 
 @ifclear autoconf
 
@@ -24,8 +24,8 @@ should configure, build, and install this package.  The following
 more-detailed instructions are generic; see the @file{README} file for
 instructions specific to this package.
 @ifclear autoconf
-Some packages provide this @file{INSTALL} file but do not implement all
-of the features documented below.  The lack of an optional feature in a
+Some packages provide this @file{README-configure} file but do not implement
+all of the features documented below.  The lack of an optional feature in a
 given package is not necessarily a bug.
 @end ifclear
 More recommendations for GNU packages can be found in

random_ioctl.c

@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) 2018 The strace developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "defs.h"
+#include "print_fields.h"
+
+#include <linux/types.h>
+#include <linux/random.h>
+
+#define XLAT_MACROS_ONLY
+# include "xlat/random_ioctl_cmds.h"
+#undef XLAT_MACROS_ONLY
+
+/*
+ * RNDGETPOOL was removed in 2.6.9, so non-ancient kernels always
+ * return -EINVAL for that.
+ */
+
+int
+random_ioctl(struct tcb *const tcp, const unsigned int code,
+	   const kernel_ulong_t arg)
+{
+	struct rand_pool_info info;
+	kernel_ulong_t buf;
+
+	switch (code) {
+	case RNDGETENTCNT:
+		if (entering(tcp))
+			return 0;
+		ATTRIBUTE_FALLTHROUGH;
+	case RNDADDTOENTCNT:
+		tprints(", ");
+		printnum_int(tcp, arg, "%d");
+		break;
+
+	case RNDADDENTROPY:
+		tprints(", ");
+		if (!umove_or_printaddr(tcp, arg, &info)) {
+			PRINT_FIELD_D("{", info, entropy_count);
+			PRINT_FIELD_D(", ", info, buf_size);
+			tprints(", buf=");
+			buf = arg + offsetof(struct rand_pool_info, buf);
+			printstrn(tcp, buf, info.buf_size);
+			tprints("}");
+		}
+		break;
+
+	/* ioctls with no parameters */
+	case RNDZAPENTCNT:
+	case RNDCLEARPOOL:
+	case RNDRESEEDCRNG:
+		break;
+	default:
+		return RVAL_DECODED;
+	}
+	return RVAL_IOCTL_DECODED;
+}

strace.c

@@ -161,10 +161,17 @@ static struct tcb *current_tcp;
 struct tcb_wait_data {
 	enum trace_event te; /**< Event passed to dispatch_event() */
 	int status;          /**< status, returned by wait4() */
+	unsigned long msg;   /**< Value returned by PTRACE_GETEVENTMSG */
 	siginfo_t si;        /**< siginfo, returned by PTRACE_GETSIGINFO */
 };
 
 static struct tcb **tcbtab;
+/*
+ * Since the queueing of tracees stops as soon as wait4() returns EAGAIN,
+ * or at least two events for a single tracee, tab_wait_tab size shouldn't
+ * exceed tcbtabsize + 1.
+ */
+static struct tcb_wait_data *tcb_wait_tab;
 static unsigned int nprocs;
 static size_t tcbtabsize;
 
@@ -750,6 +757,9 @@ expand_tcbtab(void)
 	for (tcb_ptr = tcbtab + old_tcbtabsize;
 	    tcb_ptr < tcbtab + tcbtabsize; tcb_ptr++, newtcbs++)
 		*tcb_ptr = newtcbs;
+
+	tcb_wait_tab = xreallocarray(tcb_wait_tab, sizeof(*tcb_wait_tab),
+				     tcbtabsize + 1);
 }
 
 static struct tcb *
@@ -853,6 +863,8 @@ droptcb(struct tcb *tcp)
 	if (printing_tcp == tcp)
 		printing_tcp = NULL;
 
+	list_remove(&tcp->wait_list);
+
 	memset(tcp, 0, sizeof(*tcp));
 }
 
@@ -2071,10 +2083,8 @@ maybe_switch_tcbs(struct tcb *tcp, const int pid)
 {
 	FILE *fp;
 	struct tcb *execve_thread;
-	long old_pid = 0;
+	long old_pid = tcb_wait_tab[tcp->wait_data_idx].msg;
 
-	if (ptrace(PTRACE_GETEVENTMSG, pid, NULL, &old_pid) < 0)
-		return tcp;
 	/* Avoid truncation in pid2tcb() param passing */
 	if (old_pid <= 0 || old_pid == pid)
 		return tcp;
@@ -2240,17 +2250,27 @@ print_event_exit(struct tcb *tcp)
 static const struct tcb_wait_data *
 next_event(void)
 {
-	static struct tcb_wait_data wait_data;
-
-	int pid;
-	int status;
-	struct tcb *tcp;
-	struct tcb_wait_data *wd = &wait_data;
-	struct rusage ru;
-
 	if (interrupted)
 		return NULL;
 
+	struct tcb *tcp = NULL;
+	struct list_item *elem;
+
+	static EMPTY_LIST(pending_tcps);
+	if (!list_is_empty(&pending_tcps))
+		goto next_event_get_tcp;
+
+	static struct tcb *extra_tcp;
+	static size_t wait_extra_data_idx;
+	if (extra_tcp) {
+		tcp = extra_tcp;
+		extra_tcp = NULL;
+		tcp->wait_data_idx = wait_extra_data_idx;
+
+		debug_msg("dequeued extra event for pid %u", tcp->pid);
+		goto next_event_exit;
+	}
+
 	/*
 	 * Used to exit simply when nprocs hits zero, but in this testcase:
 	 *  int main(void) { _exit(!!fork()); }
@@ -2292,8 +2312,10 @@ next_event(void)
 	 * then the system call will be interrupted and
 	 * the expiration will be handled by the signal handler.
 	 */
-	pid = wait4(-1, &status, __WALL, (cflag ? &ru : NULL));
-	const int wait_errno = errno;
+	int status;
+	struct rusage ru;
+	int pid = wait4(-1, &status, __WALL, (cflag ? &ru : NULL));
+	int wait_errno = errno;
 
 	/*
 	 * The window of opportunity to handle expirations
@@ -2309,135 +2331,194 @@ next_event(void)
 			return NULL;
 	}
 
-	if (pid < 0) {
-		if (wait_errno == EINTR) {
-			wd->te = TE_NEXT;
-			return wd;
+	size_t wait_tab_pos = 0;
+	bool wait_nohang = false;
+
+	for (;;) {
+		struct tcb_wait_data *wd;
+
+		if (pid < 0) {
+			if (wait_errno == EINTR)
+				break;
+			if (wait_nohang)
+				break;
+			if (nprocs == 0 && wait_errno == ECHILD)
+				return NULL;
+			/*
+			 * If nprocs > 0, ECHILD is not expected,
+			 * treat it as any other error here:
+			 */
+			errno = wait_errno;
+			perror_msg_and_die("wait4(__WALL)");
 		}
-		if (nprocs == 0 && wait_errno == ECHILD)
-			return NULL;
-		/*
-		 * If nprocs > 0, ECHILD is not expected,
-		 * treat it as any other error here:
-		 */
-		errno = wait_errno;
-		perror_msg_and_die("wait4(__WALL)");
-	}
 
-	wd->status = status;
+		if (!pid)
+			break;
 
-	if (pid == popen_pid) {
-		if (!WIFSTOPPED(status))
-			popen_pid = 0;
-		wd->te = TE_NEXT;
-		return wd;
-	}
+		if (pid == popen_pid) {
+			if (!WIFSTOPPED(status))
+				popen_pid = 0;
+			break;
+		}
 
-	if (debug_flag)
-		print_debug_info(pid, status);
+		if (debug_flag)
+			print_debug_info(pid, status);
 
-	/* Look up 'pid' in our table. */
-	tcp = pid2tcb(pid);
+		/* Look up 'pid' in our table. */
+		tcp = pid2tcb(pid);
 
-	if (!tcp) {
-		tcp = maybe_allocate_tcb(pid, status);
 		if (!tcp) {
-			wd->te = TE_NEXT;
-			return wd;
+			tcp = maybe_allocate_tcb(pid, status);
+			if (!tcp)
+				break;
 		}
+
+		if (cflag) {
+			struct timespec stime = {
+				.tv_sec = ru.ru_stime.tv_sec,
+				.tv_nsec = ru.ru_stime.tv_usec * 1000
+			};
+			ts_sub(&tcp->dtime, &stime, &tcp->stime);
+			tcp->stime = stime;
+		}
+
+		if (wait_tab_pos > tcbtabsize)
+			error_func_msg_and_die("Wait data storage overflow "
+					       "(wait_tab_pos %zu, nprocs %u, "
+					       "tcbtabsize %zu)", wait_tab_pos,
+					       nprocs, tcbtabsize);
+
+		wd = tcb_wait_tab + wait_tab_pos;
+		memset(wd, 0, sizeof(*wd));
+
+		if (WIFSIGNALED(status)) {
+			wd->te = TE_SIGNALLED;
+		} else if (WIFEXITED(status)) {
+			wd->te = TE_EXITED;
+		} else {
+			/*
+			 * As WCONTINUED flag has not been specified to wait4,
+			 * it cannot be WIFCONTINUED(status), so the only case
+			 * that remains is WIFSTOPPED(status).
+			 */
+
+			const unsigned int sig = WSTOPSIG(status);
+			const unsigned int event = (unsigned int) status >> 16;
+
+			switch (event) {
+			case 0:
+				/*
+				 * Is this post-attach SIGSTOP?
+				 * Interestingly, the process may stop
+				 * with STOPSIG equal to some other signal
+				 * than SIGSTOP if we happened to attach
+				 * just before the process takes a signal.
+				 */
+				if (sig == SIGSTOP &&
+				    (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)) {
+					debug_func_msg("ignored SIGSTOP on "
+						       "pid %d", tcp->pid);
+					tcp->flags &= ~TCB_IGNORE_ONE_SIGSTOP;
+					wd->te = TE_RESTART;
+				} else if (sig == syscall_trap_sig) {
+					wd->te = TE_SYSCALL_STOP;
+				} else {
+					/*
+					 * True if tracee is stopped by signal
+					 * (as opposed to "tracee received
+					 * signal").
+					 * TODO: shouldn't we check for
+					 * errno == EINVAL too?
+					 * We can get ESRCH instead, you know...
+					 */
+					bool stopped = ptrace(PTRACE_GETSIGINFO,
+						pid, 0, &wd->si) < 0;
+
+					wd->te = stopped ? TE_GROUP_STOP
+							 : TE_SIGNAL_DELIVERY_STOP;
+				}
+				break;
+			case PTRACE_EVENT_STOP:
+				/*
+				 * PTRACE_INTERRUPT-stop or group-stop.
+				 * PTRACE_INTERRUPT-stop has sig == SIGTRAP here.
+				 */
+				switch (sig) {
+				case SIGSTOP:
+				case SIGTSTP:
+				case SIGTTIN:
+				case SIGTTOU:
+					wd->te = TE_GROUP_STOP;
+					break;
+				default:
+					wd->te = TE_RESTART;
+				}
+				break;
+			case PTRACE_EVENT_EXEC:
+					/*
+					 * TODO: shouldn't we check for
+					 * errno == EINVAL here, too?
+					 * We can get ESRCH instead, you know...
+					 */
+				if (ptrace(PTRACE_GETEVENTMSG, pid, NULL,
+				    &wd->msg) < 0)
+					wd->msg = 0;
+
+				wd->te = TE_STOP_BEFORE_EXECVE;
+				break;
+			case PTRACE_EVENT_EXIT:
+				wd->te = TE_STOP_BEFORE_EXIT;
+				break;
+			default:
+				wd->te = TE_RESTART;
+			}
+		}
+
+		if (tcp->wait_list.next) {
+			wait_extra_data_idx = wait_tab_pos;
+			extra_tcp = tcp;
+			debug_func_msg("queued extra pid %d", tcp->pid);
+		} else {
+			tcp->wait_data_idx = wait_tab_pos;
+			list_append(&pending_tcps, &tcp->wait_list);
+			debug_func_msg("queued pid %d", tcp->pid);
+		}
+
+		wd->status = status;
+		wait_tab_pos++;
+
+		if (extra_tcp)
+			break;
+
+		pid = wait4(-1, &status, __WALL | WNOHANG, (cflag ? &ru : NULL));
+		wait_errno = errno;
+		wait_nohang = true;
 	}
 
+next_event_get_tcp:
+	elem = list_remove_head(&pending_tcps);
+
+	if (!elem) {
+		memset(tcb_wait_tab, 0, sizeof(*tcb_wait_tab));
+		tcb_wait_tab->te = TE_NEXT;
+
+		return tcb_wait_tab;
+	} else {
+		tcp = list_elem(elem, struct tcb, wait_list);
+		debug_func_msg("dequeued pid %d", tcp->pid);
+	}
+
+next_event_exit:
+	/* Is this the very first time we see this tracee stopped? */
+	if (tcp->flags & TCB_STARTUP)
+		startup_tcb(tcp);
+
 	clear_regs(tcp);
 
 	/* Set current output file */
 	set_current_tcp(tcp);
 
-	if (cflag) {
-		struct timespec stime = {
-			.tv_sec = ru.ru_stime.tv_sec,
-			.tv_nsec = ru.ru_stime.tv_usec * 1000
-		};
-		ts_sub(&tcp->dtime, &stime, &tcp->stime);
-		tcp->stime = stime;
-	}
-
-	if (WIFSIGNALED(status)) {
-		wd->te = TE_SIGNALLED;
-		return wd;
-	}
-
-	if (WIFEXITED(status)) {
-		wd->te = TE_EXITED;
-		return wd;
-	}
-
-	/*
-	 * As WCONTINUED flag has not been specified to wait4,
-	 * it cannot be WIFCONTINUED(status), so the only case
-	 * that remains is WIFSTOPPED(status).
-	 */
-
-	/* Is this the very first time we see this tracee stopped? */
-	if (tcp->flags & TCB_STARTUP)
-		startup_tcb(tcp);
-
-	const unsigned int sig = WSTOPSIG(status);
-	const unsigned int event = (unsigned int) status >> 16;
-
-	switch (event) {
-	case 0:
-		/*
-		 * Is this post-attach SIGSTOP?
-		 * Interestingly, the process may stop
-		 * with STOPSIG equal to some other signal
-		 * than SIGSTOP if we happened to attach
-		 * just before the process takes a signal.
-		 */
-		if (sig == SIGSTOP && (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)) {
-			debug_func_msg("ignored SIGSTOP on pid %d", tcp->pid);
-			tcp->flags &= ~TCB_IGNORE_ONE_SIGSTOP;
-			wd->te = TE_RESTART;
-		} else if (sig == syscall_trap_sig) {
-			wd->te = TE_SYSCALL_STOP;
-		} else {
-			memset(&wd->si, 0, sizeof(wd->si));
-			/*
-			 * True if tracee is stopped by signal
-			 * (as opposed to "tracee received signal").
-			 * TODO: shouldn't we check for errno == EINVAL too?
-			 * We can get ESRCH instead, you know...
-			 */
-			bool stopped = ptrace(PTRACE_GETSIGINFO, pid, 0, &wd->si) < 0;
-			wd->te = stopped ? TE_GROUP_STOP : TE_SIGNAL_DELIVERY_STOP;
-		}
-		break;
-	case PTRACE_EVENT_STOP:
-		/*
-		 * PTRACE_INTERRUPT-stop or group-stop.
-		 * PTRACE_INTERRUPT-stop has sig == SIGTRAP here.
-		 */
-		switch (sig) {
-		case SIGSTOP:
-		case SIGTSTP:
-		case SIGTTIN:
-		case SIGTTOU:
-			wd->te = TE_GROUP_STOP;
-			break;
-		default:
-			wd->te = TE_RESTART;
-		}
-		break;
-	case PTRACE_EVENT_EXEC:
-		wd->te = TE_STOP_BEFORE_EXECVE;
-		break;
-	case PTRACE_EVENT_EXIT:
-		wd->te = TE_STOP_BEFORE_EXIT;
-		break;
-	default:
-		wd->te = TE_RESTART;
-	}
-
-	return wd;
+	return tcb_wait_tab + tcp->wait_data_idx;
 }
 
 static int

strace.spec.in

@@ -91,6 +91,9 @@ echo 'END OF TEST SUITE INFORMATION'
 * @RPM_CHANGELOGTIME@ @PACKAGE_BUGREPORT@ - @PACKAGE_VERSION@-1
 - @PACKAGE_STRING@ snapshot.
 
+* Tue Oct 30 2018 Dmitry V. Levin <ldv@altlinux.org> - 4.25-1
+- v4.24 -> v4.25.
+
 * Tue Aug 14 2018 Dmitry V. Levin <ldv@altlinux.org> - 4.24-1
 - v4.23 -> v4.24.
 

test/.gitignore

@@ -1,7 +1,6 @@
 childthread
 clone
 leaderkill
-many_looping_threads
 mmap_offset_decode
 mtd
 seccomp

test/Makefile

@@ -3,8 +3,7 @@ CFLAGS += -Wall
 PROGS = \
     sig skodic clone leaderkill childthread \
     sigkill_rain wait_must_be_interruptible threaded_execve \
-    mtd ubi seccomp sfd mmap_offset_decode x32_lseek x32_mmap \
-    many_looping_threads
+    mtd ubi seccomp sfd mmap_offset_decode x32_lseek x32_mmap
 
 all: $(PROGS)
 
@@ -12,8 +11,6 @@ leaderkill: LDFLAGS += -pthread
 
 childthread: LDFLAGS += -pthread
 
-many_looping_threads: LDFLAGS += -pthread
-
 clean distclean:
 	rm -f *.o core $(PROGS) *.gdb
 

test/many_looping_threads.c

@@ -1,49 +0,0 @@
-// This testcase, when run with large number of threads
-// under stace -f, may never finish because strace does not
-// ensure any fairness in thread scheduling:
-// it restarts threads as they stop. If daughter threads crowd out
-// the "mother" and _they_ get continually restarted by strace,
-// the end of spawning loop will never be reached.
-//
-// Also, it is a testcase which triggers the
-// "strace: Exit of unknown pid 32457 seen"
-// message when on testcase exit, strace sees deaths of newly-attached
-// threads _before_ their first syscall stop.
-//
-#include <stdio.h>
-#include <pthread.h>
-#include <unistd.h>
-#include <sys/types.h>
-#include <signal.h>
-#include <stdlib.h>
-
-static int thd_no;
-
-static void *sub_thd(void *c)
-{
-	dprintf(1, "sub-thread %d created\n", ++thd_no);
-	for (;;)
-		getuid();
-	return NULL;
-}
-
-int main(int argc, char *argv[])
-{
-	int i;
-	pthread_t *thd;
-	int num_threads = 1;
-
-	if (argv[1])
-		num_threads = atoi(argv[1]);
-
-	thd = malloc(num_threads * sizeof(thd[0]));
-	dprintf(1, "test start, num_threads:%d...\n", num_threads);
-
-	for (i = 0; i < num_threads; i++) {
-		pthread_create(&thd[i], NULL, sub_thd, NULL);
-		dprintf(1, "after pthread_create\n");
-	}
-
-	/* Exit. This kills all threads */
-	return 0;
-}

tests/.gitignore

@@ -158,6 +158,7 @@ ioctl_nsfs
 ioctl_perf
 ioctl_perf-success
 ioctl_ptp
+ioctl_random
 ioctl_rtc
 ioctl_rtc-v
 ioctl_scsi
@@ -209,6 +210,7 @@ list_sigaction_signum
 llseek
 localtime
 lookup_dcookie
+looping_threads
 lseek
 lstat
 lstat64

tests/Makefile.am

@@ -129,6 +129,7 @@ check_PROGRAMS = $(PURE_EXECUTABLES) \
 	ksysent \
 	list_sigaction_signum \
 	localtime \
+	looping_threads \
 	mmsg-silent \
 	mmsg_name-v \
 	msg_control-v \
@@ -192,6 +193,7 @@ fstat64_CPPFLAGS = $(AM_CPPFLAGS) -D_FILE_OFFSET_BITS=64
 fstatat64_CPPFLAGS = $(AM_CPPFLAGS) -D_FILE_OFFSET_BITS=64
 ftruncate64_CPPFLAGS = $(AM_CPPFLAGS) -D_FILE_OFFSET_BITS=64
 localtime_LDADD = $(clock_LIBS) $(LDADD)
+looping_threads_LDADD = -lpthread $(LDADD)
 lstat64_CPPFLAGS = $(AM_CPPFLAGS) -D_FILE_OFFSET_BITS=64
 mmap64_CPPFLAGS = $(AM_CPPFLAGS) -D_FILE_OFFSET_BITS=64
 mmap64_Xabbrev_CPPFLAGS = $(AM_CPPFLAGS) -D_FILE_OFFSET_BITS=64
@@ -325,6 +327,7 @@ MISC_TESTS = \
 	interactive_block.test \
 	ksysent.test \
 	localtime.test \
+	looping_threads.test \
 	opipe.test \
 	options-syntax.test \
 	pc.test \

tests/gen_tests.in

@@ -150,6 +150,7 @@ ioctl_nbd	+ioctl.test -y
 ioctl_nsfs	+ioctl.test -esignal=none
 ioctl_perf	+ioctl.test
 ioctl_ptp 	+ioctl.test
+ioctl_random	+ioctl.test
 ioctl_rtc	+ioctl.test
 ioctl_rtc-v	+ioctl.test -v
 ioctl_scsi	+ioctl.test

tests/ioctl_random.c

@@ -0,0 +1,80 @@
+/*
+ * Check decoding of RND* commands of ioctl syscall.
+ *
+ * Copyright (c) 2018 The strace developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "tests.h"
+
+#include <stdio.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <linux/types.h>
+#include <linux/random.h>
+
+#define XLAT_MACROS_ONLY
+# include "xlat/random_ioctl_cmds.h"
+#undef XLAT_MACROS_ONLY
+
+#define RVAL_EBADF " = -1 EBADF (%m)\n"
+
+int
+main(void)
+{
+	union {
+		char c[sizeof(struct rand_pool_info) + 8];
+		struct rand_pool_info info;
+	} u;
+	struct rand_pool_info *info = &u.info;
+	int cnt = 6;
+
+	memcpy(info->buf, "12345678", 8);
+	info->buf_size = 8;
+	info->entropy_count = 3;
+
+	ioctl(-1, RNDGETENTCNT, &cnt);
+	printf("ioctl(-1, RNDGETENTCNT, %p)" RVAL_EBADF, &cnt);
+	ioctl(-1, RNDADDTOENTCNT, &cnt);
+	printf("ioctl(-1, RNDADDTOENTCNT, [6])" RVAL_EBADF);
+
+	ioctl(-1, RNDADDENTROPY, NULL);
+	printf("ioctl(-1, RNDADDENTROPY, NULL)" RVAL_EBADF);
+	ioctl(-1, RNDADDENTROPY, info);
+	printf("ioctl(-1, RNDADDENTROPY, {entropy_count=3, buf_size=8, buf=\"12345678\"})" RVAL_EBADF);
+
+	ioctl(-1, RNDZAPENTCNT);
+	printf("ioctl(-1, RNDZAPENTCNT)" RVAL_EBADF);
+	ioctl(-1, RNDCLEARPOOL);
+	printf("ioctl(-1, RNDCLEARPOOL)" RVAL_EBADF);
+	ioctl(-1, RNDRESEEDCRNG);
+	printf("ioctl(-1, RNDRESEEDCRNG)" RVAL_EBADF);
+
+	ioctl(-1, _IO('R', 0xff), NULL);
+	printf("ioctl(-1, _IOC(_IOC_NONE, %#x, 0xff, 0), 0)" RVAL_EBADF, 'R');
+
+	puts("+++ exited with 0 +++");
+	return 0;
+}

tests/looping_threads.c

@@ -0,0 +1,110 @@
+/*
+ * Check tracing of looping threads.
+ *
+ * Copyright (c) 2009-2018 The strace developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "tests.h"
+#include <assert.h>
+#include <errno.h>
+#include <pthread.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+static void *
+thread(void *arg)
+{
+	for (;;)
+		getuid();
+	return arg;
+}
+
+int
+main(int ac, const char *av[])
+{
+	assert(ac == 3);
+
+	int timeout = atoi(av[1]);
+	assert(timeout > 0);
+
+	int num_threads = atoi(av[2]);
+	assert(num_threads > 0);
+
+	/* Create a new process group.  */
+	if (setpgid(0, 0))
+		perror_msg_and_fail("setpgid");
+
+	/*
+	 * When the main process terminates, the process group becomes orphaned.
+	 * If any member of the orphaned process group is stopped, then
+	 * a SIGHUP signal followed by a SIGCONT signal is sent to each process
+	 * in the orphaned process group.
+	 * Create a process in a stopped state to activate this behaviour.
+	 */
+	pid_t stopped = fork();
+	if (stopped < 0)
+		perror_msg_and_fail("fork");
+	if (!stopped) {
+		raise(SIGSTOP);
+		_exit(0);
+	}
+
+	const sigset_t set = {};
+	const struct sigaction act = { .sa_handler = SIG_DFL };
+	if (sigaction(SIGALRM, &act, NULL))
+		perror_msg_and_fail("sigaction");
+	if (sigprocmask(SIG_SETMASK, &set, NULL))
+		perror_msg_and_fail("sigprocmask");
+	alarm(timeout);
+
+	/*
+	 * Create all threads in a subprocess, this guarantees that
+	 * their tracer will not be their parent.
+	 */
+	pid_t pid = fork();
+	if (pid < 0)
+		perror_msg_and_fail("fork");
+	if (!pid) {
+		for (int i = 0; i < num_threads; i++) {
+			pthread_t t;
+			if ((errno = pthread_create(&t, NULL, thread, NULL)))
+				perror_msg_and_fail("pthread_create #%d", i);
+		}
+
+		/* This terminates all threads.  */
+		_exit(0);
+	}
+
+	int s;
+	if (waitpid(pid, &s, 0) != pid)
+		perror_msg_and_fail("waitpid");
+
+	assert(WIFEXITED(s));
+	return WEXITSTATUS(s);
+}

tests/looping_threads.test

@@ -0,0 +1,37 @@
+#!/bin/sh
+#
+# Check tracing of looping threads.
+#
+# Copyright (c) 2009-2018 The strace developers.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+# 3. The name of the author may not be used to endorse or promote products
+#    derived from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+. "${srcdir=.}/init.sh"
+
+check_prog nproc
+timeout="$(($TIMEOUT_DURATION/10))"
+nproc="$((64+$timeout+$(nproc)))"
+
+run_prog "../$NAME" "$timeout" "$nproc"
+run_strace -f -qq -enone -esignal=none $args

tests/pure_executables.list

@@ -121,6 +121,7 @@ ioctl_mtd
 ioctl_nbd
 ioctl_perf
 ioctl_ptp
+ioctl_random
 ioctl_rtc
 ioctl_scsi
 ioctl_sg_io_v3

xlat/random_ioctl_cmds.in

@@ -0,0 +1,7 @@
+RNDGETENTCNT		_IOR( 'R', 0x00, int )
+RNDADDTOENTCNT		_IOW( 'R', 0x01, int )
+RNDGETPOOL		_IOR( 'R', 0x02, int [2] )
+RNDADDENTROPY		_IOW( 'R', 0x03, int [2] )
+RNDZAPENTCNT		_IO( 'R', 0x04 )
+RNDCLEARPOOL		_IO( 'R', 0x06 )
+RNDRESEEDCRNG		_IO( 'R', 0x07 )