diff options
| author | Alex Bennée <alex.bennee@linaro.org> | 2022-10-04 12:52:21 +0100 |
|---|---|---|
| committer | Alex Bennée <alex.bennee@linaro.org> | 2022-10-06 11:53:41 +0100 |
| commit | f7e15affa8e574a800180de3bde1a6462aec7241 (patch) | |
| tree | c759a5deb49756097f301652837b14ffc91ef6b2 | |
| parent | 37e62694e4bcc937c8c5fa6153302a5451fb12c5 (diff) | |
plugins: add [pre|post]fork helpers to linux-user
Special care needs to be taken in ensuring locks are in a consistent
state across fork events. Add helpers so the plugin system can ensure
that.
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Fixes: https://gitlab.com/qemu-project/qemu/-/issues/358
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Tested-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20221004115221.2174499-1-alex.bennee@linaro.org>
| -rw-r--r-- | include/qemu/plugin.h | 24 | ||||
| -rw-r--r-- | linux-user/main.c | 2 | ||||
| -rw-r--r-- | plugins/core.c | 20 |
3 files changed, 46 insertions, 0 deletions
diff --git a/include/qemu/plugin.h b/include/qemu/plugin.h index 145f8a221a..a772e14193 100644 --- a/include/qemu/plugin.h +++ b/include/qemu/plugin.h @@ -224,6 +224,23 @@ void qemu_plugin_disable_mem_helpers(CPUState *cpu); */ void qemu_plugin_user_exit(void); +/** + * qemu_plugin_user_prefork_lock(): take plugin lock before forking + * + * This is a user-mode only helper to take the internal plugin lock + * before a fork event. This is ensure a consistent lock state + */ +void qemu_plugin_user_prefork_lock(void); + +/** + * qemu_plugin_user_postfork(): reset the plugin lock + * @is_child: is this thread the child + * + * This user-mode only helper resets the lock state after a fork so we + * can continue using the plugin interface. + */ +void qemu_plugin_user_postfork(bool is_child); + #else /* !CONFIG_PLUGIN */ static inline void qemu_plugin_add_opts(void) @@ -287,6 +304,13 @@ static inline void qemu_plugin_disable_mem_helpers(CPUState *cpu) static inline void qemu_plugin_user_exit(void) { } + +static inline void qemu_plugin_user_prefork_lock(void) +{ } + +static inline void qemu_plugin_user_postfork(bool is_child) +{ } + #endif /* !CONFIG_PLUGIN */ #endif /* QEMU_PLUGIN_H */ diff --git a/linux-user/main.c b/linux-user/main.c index 88fccfe261..a17fed045b 100644 --- a/linux-user/main.c +++ b/linux-user/main.c @@ -142,10 +142,12 @@ void fork_start(void) start_exclusive(); mmap_fork_start(); cpu_list_lock(); + qemu_plugin_user_prefork_lock(); } void fork_end(int child) { + qemu_plugin_user_postfork(child); mmap_fork_end(child); if (child) { CPUState *cpu, *next_cpu; diff --git a/plugins/core.c b/plugins/core.c index c3ae284994..ccb770a485 100644 --- a/plugins/core.c +++ b/plugins/core.c @@ -527,6 +527,26 @@ void qemu_plugin_user_exit(void) } /* + * Helpers for *-user to ensure locks are sane across fork() events. + */ + +void qemu_plugin_user_prefork_lock(void) +{ + qemu_rec_mutex_lock(&plugin.lock); +} + +void qemu_plugin_user_postfork(bool is_child) +{ + if (is_child) { + /* should we just reset via plugin_init? */ + qemu_rec_mutex_init(&plugin.lock); + } else { + qemu_rec_mutex_unlock(&plugin.lock); + } +} + + +/* * Call this function after longjmp'ing to the main loop. It's possible that the * last instruction of a TB might have used helpers, and therefore the * "disable" instruction will never execute because it ended up as dead code. |