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Re: [Qemu-devel] [PATCH v4] block: replace fprintf(stderr, ...) with err
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH v4] block: replace fprintf(stderr, ...) with error_report() |
Date: |
Mon, 26 May 2014 17:02:46 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) |
Stefan Hajnoczi <address@hidden> writes:
> On Mon, May 26, 2014 at 09:44:03AM +0800, Le Tan wrote:
>> Replace fprintf(stderr,...) with error_report() in files block/*, block.c,
>> block-migration.c and blockdev.c. The trailing "\n"s of the @fmt argument
>> have been removed because @fmt of error_report() should not contain newline.
>>
>> Signed-off-by: Le Tan <address@hidden>
>> ---
>> block-migration.c | 6 +--
>> block.c | 4 +-
>> block/qcow2-refcount.c | 115 +++++++++++++++++++++---------------------
>> block/qcow2.c | 16 +++---
>> block/raw-posix.c | 8 ++-
>> block/raw-win32.c | 6 +--
>> block/ssh.c | 2 +-
>> block/vdi.c | 14 +++---
>> block/vmdk.c | 15 +++---
>> block/vpc.c | 4 +-
>> block/vvfat.c | 129
>> ++++++++++++++++++++++++------------------------
>> blockdev.c | 6 +--
>> 12 files changed, 159 insertions(+), 166 deletions(-)
>
> There is one thing that worries me about this:
>
> error_report() assumes that the QEMU global mutex is held in order to
> access the "current monitor".
Global variable cur_mon, non-null while we're executing a monitor
command.
> This is problematic for code in the read/write/flush path (like qcow2
> refcount allocation) since it can be invoked from a virtio-blk
> data-plane thread (where the QEMU global mutex is not held).
error_report() reports to the current monitor when "in monitor context",
i.e. while executing a monitor command, i.e. while cur_mon isn't null.
Can we ever be in monitor context (cur_mon not null) without holding the
global mutex?
> For the time being, I prefer keeping the fprintf(). In the long term we
> need to decide:
> 1. Some functions should use Error * to report errors.
> 2. Some functions really produce their own output but it probably
> shouldn't go to the monitor.
> 3. The remaining functions may really be error_report() candidates.
0. Figure out what rules apply to cur_mon with respect to the global
mutex.
- [Qemu-devel] [PATCH v4] block: replace fprintf(stderr, ...) with error_report(), Le Tan, 2014/05/25
- Re: [Qemu-devel] [PATCH v4] block: replace fprintf(stderr, ...) with error_report(), Stefan Hajnoczi, 2014/05/26
- Re: [Qemu-devel] [PATCH v4] block: replace fprintf(stderr, ...) with error_report(),
Markus Armbruster <=
- Re: [Qemu-devel] [PATCH v4] block: replace fprintf(stderr, ...) with error_report(), Kevin Wolf, 2014/05/26
- Re: [Qemu-devel] [PATCH v4] block: replace fprintf(stderr, ...) with error_report(), Markus Armbruster, 2014/05/26
- Re: [Qemu-devel] [PATCH v4] block: replace fprintf(stderr, ...) with error_report(), Stefan Hajnoczi, 2014/05/27
- Re: [Qemu-devel] [PATCH v4] block: replace fprintf(stderr, ...) with error_report(), Markus Armbruster, 2014/05/27