Stefan Hajnoczi <stefa...@gmail.com> 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 <tamlokv...@gmail.com> >> --- >> 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.
