67 lines
2.1 KiB
Diff
67 lines
2.1 KiB
Diff
From a729d2730d9d30f6610e43f070cedd1d60ba022f Mon Sep 17 00:00:00 2001
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From: qihao <qihao@cmss.chinamobile.com>
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Date: Thu, 30 Mar 2023 17:58:32 +0800
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Subject: [PATCH] plugins: make qemu_plugin_user_exit's locking order
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consistent with fork_start's
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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cheery-pick from 2bbbc1be8d9a21b25d0c80b9a7345074d54abd51
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To fix potential deadlocks as reported by tsan.
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Signed-off-by: qihao_yewu <qihao_yewu@cmss.chinamobile.com>
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Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
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Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
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Signed-off-by: Emilio Cota <cota@braap.org>
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Message-Id: <20230111151628.320011-6-cota@braap.org>
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Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
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Message-Id: <20230124180127.1881110-31-alex.bennee@linaro.org>
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---
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plugins/core.c | 14 +++++++++++---
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1 file changed, 11 insertions(+), 3 deletions(-)
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diff --git a/plugins/core.c b/plugins/core.c
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index 792262da08..e935e3c0c9 100644
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--- a/plugins/core.c
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+++ b/plugins/core.c
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@@ -500,10 +500,18 @@ void qemu_plugin_user_exit(void)
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enum qemu_plugin_event ev;
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CPUState *cpu;
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- QEMU_LOCK_GUARD(&plugin.lock);
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+ /*
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+ * Locking order: we must acquire locks in an order that is consistent
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+ * with the one in fork_start(). That is:
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+ * - start_exclusive(), which acquires qemu_cpu_list_lock,
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+ * must be called before acquiring plugin.lock.
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+ * - tb_flush(), which acquires mmap_lock(), must be called
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+ * while plugin.lock is not held.
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+ */
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start_exclusive();
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+ qemu_rec_mutex_lock(&plugin.lock);
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/* un-register all callbacks except the final AT_EXIT one */
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for (ev = 0; ev < QEMU_PLUGIN_EV_MAX; ev++) {
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if (ev != QEMU_PLUGIN_EV_ATEXIT) {
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@@ -514,12 +522,12 @@ void qemu_plugin_user_exit(void)
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}
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}
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- tb_flush(current_cpu);
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-
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CPU_FOREACH(cpu) {
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qemu_plugin_disable_mem_helpers(cpu);
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}
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+ qemu_rec_mutex_unlock(&plugin.lock);
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+ tb_flush(current_cpu);
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end_exclusive();
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/* now it's safe to handle the exit case */
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--
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2.27.0
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