Commit Graph

11 Commits

Author SHA1 Message Date
Emilio G. Cota 068a5ea02f qom: convert the CPU list to RCU
Iterating over the list without using atomics is undefined behaviour,
since the list can be modified concurrently by other threads (e.g.
every time a new thread is created in user-mode).

Fix it by implementing the CPU list as an RCU QTAILQ. This requires
a little bit of extra work to traverse list in reverse order (see
previous patch), but other than that the conversion is trivial.

Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <20180819091335.22863-12-cota@braap.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-08-23 18:46:25 +02:00
Paolo Bonzini 14e6fe12a7 *_run_on_cpu: introduce run_on_cpu_data type
This changes the *_run_on_cpu APIs (and helpers) to pass data in a
run_on_cpu_data type instead of a plain void *. This is because we
sometimes want to pass a target address (target_ulong) and this fails on
32 bit hosts emulating 64 bit guests.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20161027151030.20863-24-alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-10-31 15:00:25 +01:00
Paolo Bonzini c265e976f4 cpus-common: lock-free fast path for cpu_exec_start/end
Set cpu->running without taking the cpu_list lock, only requiring it if
there is a concurrent exclusive section.  This requires adding a new
field to CPUState, which records whether a running CPU is being counted
in pending_cpus.

When an exclusive section is started concurrently with cpu_exec_start,
cpu_exec_start can use the new field to determine if it has to wait for
the end of the exclusive section.  Likewise, cpu_exec_end can use it to
see if start_exclusive is waiting for that CPU.

This a separate patch for easier bisection of issues.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-27 11:57:30 +02:00
Paolo Bonzini 53f5ed9506 cpus-common: Introduce async_safe_run_on_cpu()
Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-27 11:57:30 +02:00
Paolo Bonzini 758e1b2b62 cpus-common: simplify locking for start_exclusive/end_exclusive
It is not necessary to hold qemu_cpu_list_mutex throughout the
exclusive section, because no other exclusive section can run
while pending_cpus != 0.

exclusive_idle() is called in cpu_exec_start(), and that prevents
any CPUs created after start_exclusive() from entering cpu_exec()
during an exclusive section.

Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-27 11:57:30 +02:00
Paolo Bonzini cf07da65f3 cpus-common: remove redundant call to exclusive_idle()
No need to call exclusive_idle() from cpu_exec_end since it is done
immediately afterwards in cpu_exec_start.  Any exclusive section could
run as soon as cpu_exec_end leaves, because cpu->running is false and the
mutex is not taken, so the call does not add any protection either.

Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-27 11:57:30 +02:00
Paolo Bonzini c978b31687 cpus-common: always defer async_run_on_cpu work items
async_run_on_cpu is only called from the I/O thread, not from CPU threads,
so it doesn't make any difference.  It will make a difference however
for async_safe_run_on_cpu.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-27 11:57:30 +02:00
Paolo Bonzini ab129972c8 cpus-common: move exclusive work infrastructure from linux-user
This will serve as the base for async_safe_run_on_cpu.  Because
start_exclusive uses CPU_FOREACH, merge exclusive_lock with
qemu_cpu_list_lock: together with a call to exclusive_idle (via
cpu_exec_start/end) in cpu_list_add, this protects exclusive work
against concurrent CPU addition and removal.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-27 11:57:30 +02:00
Paolo Bonzini 0e55539c07 cpus-common: fix uninitialized variable use in run_on_cpu
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-27 11:57:30 +02:00
Sergey Fedorov d148d90ee8 cpus-common: move CPU work item management to common code
Make CPU work core functions common between system and user-mode
emulation. User-mode does not use run_on_cpu, so do not implement it.

Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com>
Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <1470158864-17651-10-git-send-email-alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-27 11:57:30 +02:00
Paolo Bonzini 267f685b8b cpus-common: move CPU list management to common code
Add a mutex for the CPU list to system emulation, as it will be used to
manage safe work.  Abstract manipulation of the CPU list in new functions
cpu_list_add and cpu_list_remove.

Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-27 11:57:29 +02:00