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linux-user: Hold the fd-trans lock across fork

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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: c093364f4d "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>
This commit is contained in:
Geoffrey Thomas 2025-03-14 08:47:42 -04:00 committed by Richard Henderson
parent 91748d50c7
commit e4e839b2ee
2 changed files with 12 additions and 0 deletions
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10
linux-user/fd-trans.h
View File

@ -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) {

2
linux-user/main.c
View File

@ -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) {