From: Geoffrey Thomas <geo...@ldpreload.com> 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-sta...@nongnu.org Signed-off-by: Geoffrey Thomas <geo...@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.hender...@linaro.org> Signed-off-by: Richard Henderson <richard.hender...@linaro.org> Message-ID: <20250314124742.4965-1-geo...@ldpreload.com> (cherry picked from commit e4e839b2eeea5745c48ce47144c7842eb7cd455f) Signed-off-by: Michael Tokarev <m...@tls.msk.ru> diff --git a/linux-user/fd-trans.h b/linux-user/fd-trans.h index 910faaf237..e14f96059c 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 e2ec5970be..2cd867491b 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) { -- 2.47.2
