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[PATCH v2 30/35] plugins: make qemu_plugin_user_exit's locking order con
From: |
Alex Bennée |
Subject: |
[PATCH v2 30/35] plugins: make qemu_plugin_user_exit's locking order consistent with fork_start's |
Date: |
Tue, 24 Jan 2023 18:01:22 +0000 |
From: Emilio Cota <cota@braap.org>
To fix potential deadlocks as reported by tsan.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Emilio Cota <cota@braap.org>
Message-Id: <20230111151628.320011-6-cota@braap.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
plugins/core.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/plugins/core.c b/plugins/core.c
index ccb770a485..728bacef95 100644
--- a/plugins/core.c
+++ b/plugins/core.c
@@ -500,10 +500,17 @@ void qemu_plugin_user_exit(void)
enum qemu_plugin_event ev;
CPUState *cpu;
- QEMU_LOCK_GUARD(&plugin.lock);
-
+ /*
+ * Locking order: we must acquire locks in an order that is consistent
+ * with the one in fork_start(). That is:
+ * - start_exclusive(), which acquires qemu_cpu_list_lock,
+ * must be called before acquiring plugin.lock.
+ * - tb_flush(), which acquires mmap_lock(), must be called
+ * while plugin.lock is not held.
+ */
start_exclusive();
+ qemu_rec_mutex_lock(&plugin.lock);
/* un-register all callbacks except the final AT_EXIT one */
for (ev = 0; ev < QEMU_PLUGIN_EV_MAX; ev++) {
if (ev != QEMU_PLUGIN_EV_ATEXIT) {
@@ -513,13 +520,12 @@ void qemu_plugin_user_exit(void)
}
}
}
-
- tb_flush(current_cpu);
-
CPU_FOREACH(cpu) {
qemu_plugin_disable_mem_helpers(cpu);
}
+ qemu_rec_mutex_unlock(&plugin.lock);
+ tb_flush(current_cpu);
end_exclusive();
/* now it's safe to handle the exit case */
--
2.34.1
- [PATCH v2 19/35] docs: add hotlinks to about preface text, (continued)
- [PATCH v2 19/35] docs: add hotlinks to about preface text, Alex Bennée, 2023/01/24
- [PATCH v2 28/35] thread: de-const qemu_spin_destroy, Alex Bennée, 2023/01/24
- [PATCH v2 34/35] cpu-exec: assert that plugin_mem_cbs is NULL after execution, Alex Bennée, 2023/01/24
- [PATCH v2 24/35] semihosting: add O_BINARY flag in host_open for NT compatibility, Alex Bennée, 2023/01/24
- [PATCH v2 25/35] tests/tcg: add memory-sve test for aarch64, Alex Bennée, 2023/01/24
- [PATCH v2 35/35] plugins: Iterate on cb_lists in qemu_plugin_user_exit, Alex Bennée, 2023/01/24
- [PATCH v2 27/35] util/qht: add missing atomic_set(hashes[i]), Alex Bennée, 2023/01/24
- [PATCH v2 30/35] plugins: make qemu_plugin_user_exit's locking order consistent with fork_start's,
Alex Bennée <=
- [PATCH v2 13/35] tests/docker: Install flex in debian-tricore-cross, Alex Bennée, 2023/01/24
- [PATCH v2 23/35] semihosting: Write back semihosting data before completion callback, Alex Bennée, 2023/01/24
- [PATCH v2 17/35] gitlab: wrap up test results for custom runners, Alex Bennée, 2023/01/24
- [PATCH v2 33/35] tcg: exclude non-memory effecting helpers from instrumentation, Alex Bennée, 2023/01/24
- [PATCH v2 20/35] docs: add a new section to outline emulation support, Alex Bennée, 2023/01/24
- [PATCH v2 21/35] semihosting: add semihosting section to the docs, Alex Bennée, 2023/01/24
- [PATCH v2 16/35] tests/tcg: Use SIGKILL for timeout, Alex Bennée, 2023/01/24