On 9/25/24 00:43, Ilya Leoshkevich wrote:
On Tue, 2024-09-24 at 13:46 +0200, Richard Henderson wrote:
On 9/23/24 18:12, Ilya Leoshkevich wrote:
Hi,
On reporting a breakpoint in a non-non-stop mode, GDB remotes must
stop
all threads. Currently qemu-user doesn't do that, breaking the
debugging session for at least two reasons: concurrent access to
the
GDB socket, and an assertion within GDB [1].
This series fixes this by importing pause_all_vcpus() from qemu-
system.
This in turn requires introducing BQL and a few stubs to qemu-user.
I would have expected you to reuse (some portion of) start_exclusive,
which is already
part of qemu-user. Is there a reason you chose a solution which
requires...
replay: Add replay_mutex_{lock,unlock}() stubs for qemu-user
qemu-timer: Provide qemu_clock_enable() stub for qemu-user
cpu: Use BQL in qemu-user
all sorts of other infrastructure?
r~
I don't think start_exclusive() would protect the gdb socket from
concurrent accesses (e.g., if two threads are simultaneously stopped).
Of course it would, otherwise "exclusive" has no meaning.
All other cpus are blocked in exclusive_idle().
Importantly, no cpus are blocked in syscalls, where the kernel can modify memory behind
gdbstub's back (e.g. read). I think considering "in_syscall" to be "paused" a mistake.
r~
