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| author | Geoffrey Thomas <geofft@ldpreload.com> | 2025-03-14 08:47:42 -0400 |
|---|---|---|
| committer | Richard Henderson <richard.henderson@linaro.org> | 2025-07-10 13:49:03 -0600 |
| commit | e4e839b2eeea5745c48ce47144c7842eb7cd455f (patch) | |
| tree | 625dcbd28f8e2d2bd4d6e657069f0386be9fbdad | |
| parent | 91748d50c7ef4addcc9302160a4b8b3c63d5d024 (diff) | |
| download | qemu-e4e839b2eeea5745c48ce47144c7842eb7cd455f.zip qemu-e4e839b2eeea5745c48ce47144c7842eb7cd455f.tar.gz qemu-e4e839b2eeea5745c48ce47144c7842eb7cd455f.tar.bz2 | |
linux-user: Hold the fd-trans lock across fork
If another thread is holding target_fd_trans_lock during a fork,
then the lock becomes permanently locked in the child and the
emulator deadlocks at the next interaction with the fd-trans table.
As with other locks, acquire the lock in fork_start() and release
it in fork_end().
Cc: qemu-stable@nongnu.org
Signed-off-by: Geoffrey Thomas <geofft@ldpreload.com>
Fixes: c093364f4d91 "fd-trans: Fix race condition on reallocation of the translation table."
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2846
Buglink: https://github.com/astral-sh/uv/issues/6105
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20250314124742.4965-1-geofft@ldpreload.com>
| -rw-r--r-- | linux-user/fd-trans.h | 10 | ||||
| -rw-r--r-- | linux-user/main.c | 2 |
2 files changed, 12 insertions, 0 deletions
diff --git a/linux-user/fd-trans.h b/linux-user/fd-trans.h index 910faaf..e14f960 100644 --- a/linux-user/fd-trans.h +++ b/linux-user/fd-trans.h @@ -36,6 +36,16 @@ static inline void fd_trans_init(void) qemu_mutex_init(&target_fd_trans_lock); } +static inline void fd_trans_prefork(void) +{ + qemu_mutex_lock(&target_fd_trans_lock); +} + +static inline void fd_trans_postfork(void) +{ + qemu_mutex_unlock(&target_fd_trans_lock); +} + static inline TargetFdDataFunc fd_trans_target_to_host_data(int fd) { if (fd < 0) { diff --git a/linux-user/main.c b/linux-user/main.c index a9142ee..f4f2007 100644 --- a/linux-user/main.c +++ b/linux-user/main.c @@ -149,12 +149,14 @@ void fork_start(void) cpu_list_lock(); qemu_plugin_user_prefork_lock(); gdbserver_fork_start(); + fd_trans_prefork(); } void fork_end(pid_t pid) { bool child = pid == 0; + fd_trans_postfork(); qemu_plugin_user_postfork(child); mmap_fork_end(child); if (child) { |