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Max Reitz f4be822519 coroutine-sigaltstack: Add SIGUSR2 mutex 
Disposition (action) for any given signal is global for the process.
When two threads run coroutine-sigaltstack's qemu_coroutine_new()
concurrently, they may interfere with each other: One of them may revert
the SIGUSR2 handler to SIG_DFL, between the other thread (a) setting up
coroutine_trampoline() as the handler and (b) raising SIGUSR2.  That
SIGUSR2 will then terminate the QEMU process abnormally.

We have to ensure that only one thread at a time can modify the
process-global SIGUSR2 handler.  To do so, wrap the whole section where
that is done in a mutex.

Alternatively, we could for example have the SIGUSR2 handler always be
coroutine_trampoline(), so there would be no need to invoke sigaction()
in qemu_coroutine_new().  Laszlo has posted a patch to do so here:

  https://lists.nongnu.org/archive/html/qemu-devel/2021-01/msg05962.html

However, given that coroutine-sigaltstack is more of a fallback
implementation for platforms that do not support ucontext, that change
may be a bit too invasive to be comfortable with it.  The mutex proposed
here may negatively impact performance, but the change is much simpler.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20210125120305.19520-1-mreitz@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
2021-01-26 14:36:37 +01:00
..
aio-posix.c qmp: Move dispatcher to a coroutine 2020-10-09 07:08:20 +02:00
aio-posix.h aio-posix: remove idle poll handlers to improve scalability 2020-03-09 16:45:16 +00:00
aio-wait.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
aio-win32.c qmp: fix aio_poll() assertion failure on Windows 2020-11-03 16:24:56 +01:00
aiocb.c
async.c util/async: Add aio_co_reschedule_self() 2020-10-09 07:08:20 +02:00
atomic64.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
base64.c nomaintainer: Fix Lesser GPL version number 2020-11-15 17:04:40 +01:00
bitmap.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
bitops.c
block-helpers.c block: move logical block size check function to a common utility function 2020-10-23 13:42:16 +01:00
block-helpers.h block: move logical block size check function to a common utility function 2020-10-23 13:42:16 +01:00
buffer.c nomaintainer: Fix Lesser GPL version number 2020-11-15 17:04:40 +01:00
bufferiszero.c util/bufferiszero: improve avx2 accelerator 2020-04-01 14:24:03 -04:00
cacheflush.c util/cacheflush: Fix error generated by clang 2021-01-21 13:00:41 +01:00
cacheinfo.c util: Enhance flush_icache_range with separate data pointer 2021-01-07 05:09:41 -10:00
compatfd.c util/compatfd.c: Only include <sys/syscall.h> if CONFIG_SIGNALFD 2020-07-13 14:36:10 +01:00
coroutine-sigaltstack.c coroutine-sigaltstack: Add SIGUSR2 mutex 2021-01-26 14:36:37 +01:00
coroutine-ucontext.c Remove the CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE switch 2020-07-13 11:40:52 +02:00
coroutine-win32.c
crc32c.c Include qemu-common.h exactly where needed 2019-06-12 13:20:20 +02:00
crc-ccitt.c util: Add CRC16 (CCITT) calculation routines 2021-01-24 20:10:54 +01:00
cutils.c util/cutils: Fix Coverity array overrun in freq_to_str() 2020-11-17 12:56:32 +00:00
dbus.c util: add dbus helper unit 2020-01-06 18:41:32 +04:00
drm.c util/drm: make portable by avoiding struct dirent d_type 2020-07-13 14:36:10 +01:00
envlist.c Include qemu-common.h exactly where needed 2019-06-12 13:20:20 +02:00
error.c error: make Error **errp const where it is appropriate 2019-12-18 08:36:16 +01:00
event_notifier-posix.c event_notifier: avoid dandling file descriptor in event_notifier_cleanup 2019-10-24 19:26:52 +02:00
event_notifier-win32.c
fdmon-epoll.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
fdmon-io_uring.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
fdmon-poll.c fdmon-poll: reset npfd when upgrading to fdmon-epoll 2020-09-23 13:45:52 +01:00
fifo8.c Include migration/vmstate.h less 2019-08-16 13:31:52 +02:00
filemonitor-inotify.c nomaintainer: Fix Lesser GPL version number 2020-11-15 17:04:40 +01:00
filemonitor-stub.c nomaintainer: Fix Lesser GPL version number 2020-11-15 17:04:40 +01:00
getauxval.c util/getauxval: Porting to FreeBSD getauxval feature 2020-06-26 06:45:29 -04:00
guest-random.c replay: record and replay random number sources 2020-01-07 12:08:39 +01:00
hbitmap.c block/dirty-bitmap: improve _next_dirty_area API 2020-03-18 14:03:46 -04:00
hexdump.c util/hexdump: introduce qemu_hexdump_line() 2020-09-29 02:14:30 -04:00
host-utils.c
id.c chardev: generate an internal id when none given 2020-01-07 16:50:09 +04:00
iov.c util/iov: add iov_discard_undo() 2020-09-23 13:41:58 +01:00
iova-tree.c
keyval.c keyval: Use GString to accumulate value strings 2020-12-19 10:39:23 +01:00
lockcnt.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
log.c nomaintainer: Fix Lesser GPL version number 2020-11-15 17:04:40 +01:00
main-loop.c cfi: Initial support for cfi-icall in QEMU 2021-01-02 21:03:35 +01:00
memfd.c linux-user: add memfd_create 2019-09-11 08:46:17 +02:00
meson.build util: Add CRC16 (CCITT) calculation routines 2021-01-24 20:10:54 +01:00
mmap-alloc.c core: replace getpagesize() with qemu_real_host_page_size 2019-10-26 15:38:06 +02:00
module.c modules: turn off lazy binding 2020-10-29 06:37:24 +01:00
notify.c xen / notify: introduce a new XenWatchList abstraction 2019-09-24 12:18:47 +01:00
nvdimm-utils.c Clean up includes 2020-12-10 17:16:44 +01:00
osdep.c Pull request trivial patches 20200919 2020-09-22 15:42:23 +01:00
oslib-posix.c util/oslib: Assert qemu_try_memalign() alignment is a power of 2 2021-01-07 05:09:06 -10:00
oslib-win32.c util/oslib-win32: Fix _aligned_malloc() arguments order 2021-01-11 14:59:21 +01:00
pagesize.c
path.c util/path: Do not cache all filenames at startup 2019-06-24 22:19:30 +02:00
qdist.c
qemu-co-shared-resource.c util: introduce SharedResource 2019-10-28 11:22:31 +01:00
qemu-config.c qapi: Use QAPI_LIST_PREPEND() where possible 2020-12-19 10:20:14 +01:00
qemu-coroutine-io.c yield_until_fd_readable: make it work with any AioContect 2019-10-25 14:38:29 +02:00
qemu-coroutine-lock.c coroutine: let CoQueue wake up outside a coroutine 2020-11-04 08:02:24 +01:00
qemu-coroutine-sleep.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
qemu-coroutine.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
qemu-error.c monitor: Use getter/setter functions for cur_mon 2020-10-09 07:08:19 +02:00
qemu-openpty.c util/qemu-openpty.c: Don't assume pty.h is glibc-only 2020-07-13 14:36:09 +01:00
qemu-option.c qemu-option: warn for short-form boolean options 2021-01-23 15:55:08 -05:00
qemu-print.c monitor: Use getter/setter functions for cur_mon 2020-10-09 07:08:19 +02:00
qemu-progress.c util/: fix some comment spelling errors 2020-09-17 20:38:42 +02:00
qemu-sockets.c sockets: Make abstract UnixSocketAddress depend on CONFIG_LINUX 2020-11-03 13:17:25 +00:00
qemu-thread-common.h
qemu-thread-posix.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
qemu-thread-win32.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
qemu-timer-common.c semihosting: Implement SYS_ELAPSED and SYS_TICKFREQ 2021-01-18 10:05:06 +00:00
qemu-timer.c cpus: prepare new CpusAccel cpu accelerator interface 2020-10-05 16:41:22 +02:00
qht.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
qsp.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
range.c
rcu.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
readline.c readline: Fix possible array index out of bounds in readline_hist_add() 2021-01-04 11:13:39 +00:00
selfmap.c linux-user: factor out reading of /proc/self/maps 2020-04-07 16:19:49 +01:00
stats64.c qemu/atomic.h: rename atomic_ to qatomic_ 2020-09-23 16:07:44 +01:00
sys_membarrier.c
systemd.c tools: Fix use of fcntl(F_SETFD) during socket activation 2020-05-04 14:54:35 -05:00
thread-pool.c lockable: replaced locks with lock guard macros where appropriate 2020-05-04 16:07:43 +01:00
throttle.c Remove superfluous timer_del() calls 2021-01-08 15:13:38 +00:00
timed-average.c
trace-events util/vfio-helpers: Convert vfio_dump_mapping to trace events 2020-11-03 19:06:23 +00:00
trace.h trace: switch position of headers to what Meson requires 2020-08-21 06:18:24 -04:00
unicode.c
uri.c
uuid.c Include qemu-common.h exactly where needed 2019-06-12 13:20:20 +02:00
vfio-helpers.c Pull request for 5.2 2020-11-23 13:03:13 +00:00
vhost-user-server.c util/vhost-user-server: move header to include/ 2020-10-23 13:42:16 +01:00
yank.c Introduce yank feature 2021-01-13 10:21:17 +01:00