| Message ID | 20220706201533.289775-15-eesposit@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | job: replace AioContext lock with job_mutex | expand |
On 7/6/22 23:15, Emanuele Giuseppe Esposito wrote: > In order to make it thread safe, implement a "fake rwlock", > where we allow reads under BQL *or* job_mutex held, but > writes only under BQL *and* job_mutex. > > The only write we have is in child_job_set_aio_ctx also in job_create of course, but it seems safe anyway > , which always > happens under drain (so the job is paused). > For this reason, introduce job_set_aio_context and make sure that > the context is set under BQL, job_mutex and drain. > Also make sure all other places where the aiocontext is read > are protected. > > Note: at this stage, job_{lock/unlock} and job lock guard macros > are *nop*. > > Suggested-by: Paolo Bonzini <pbonzini@redhat.com> > Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> > --- > block/replication.c | 6 ++++-- > blockjob.c | 3 ++- > include/qemu/job.h | 19 ++++++++++++++++++- > job.c | 12 ++++++++++++ > 4 files changed, 36 insertions(+), 4 deletions(-) > > diff --git a/block/replication.c b/block/replication.c > index 55c8f894aa..2189863df1 100644 > --- a/block/replication.c > +++ b/block/replication.c > @@ -148,8 +148,10 @@ static void replication_close(BlockDriverState *bs) > } > if (s->stage == BLOCK_REPLICATION_FAILOVER) { > commit_job = &s->commit_job->job; > - assert(commit_job->aio_context == qemu_get_current_aio_context()); > - job_cancel_sync(commit_job, false); > + WITH_JOB_LOCK_GUARD() { > + assert(commit_job->aio_context == qemu_get_current_aio_context()); > + job_cancel_sync_locked(commit_job, false); > + } > } > > if (s->mode == REPLICATION_MODE_SECONDARY) { > diff --git a/blockjob.c b/blockjob.c > index bce05a9096..0d120ed126 100644 > --- a/blockjob.c > +++ b/blockjob.c > @@ -166,12 +166,13 @@ static void child_job_set_aio_ctx(BdrvChild *c, AioContext *ctx, > bdrv_set_aio_context_ignore(sibling->bs, ctx, ignore); > } > > - job->job.aio_context = ctx; > + job_set_aio_context(&job->job, ctx); > } > > static AioContext *child_job_get_parent_aio_context(BdrvChild *c) > { > BlockJob *job = c->opaque; > + assert(qemu_in_main_thread()); > > return job->job.aio_context; > } > diff --git a/include/qemu/job.h b/include/qemu/job.h > index 5709e8d4a8..c144aabefc 100644 > --- a/include/qemu/job.h > +++ b/include/qemu/job.h > @@ -77,7 +77,12 @@ typedef struct Job { > > /** Protected by AioContext lock */ > > - /** AioContext to run the job coroutine in */ > + /** > + * AioContext to run the job coroutine in. > + * This field can be read when holding either the BQL (so we are in > + * the main loop) or the job_mutex. > + * It can be only written when we hold *both* BQL and job_mutex. > + */ > AioContext *aio_context; > > /** Reference count of the block job */ > @@ -741,4 +746,16 @@ int job_finish_sync(Job *job, void (*finish)(Job *, Error **errp), > int job_finish_sync_locked(Job *job, void (*finish)(Job *, Error **errp), > Error **errp); > > +/** > + * Sets the @job->aio_context. > + * Called with job_mutex *not* held. > + * > + * This function must run in the main thread to protect against > + * concurrent read in job_finish_sync_locked(), > + * takes the job_mutex lock to protect against the read in > + * job_do_yield_locked(), and must be called when the coroutine > + * is quiescent. > + */ > +void job_set_aio_context(Job *job, AioContext *ctx); > + > #endif > diff --git a/job.c b/job.c > index 405f39566b..66cae82593 100644 > --- a/job.c > +++ b/job.c > @@ -394,6 +394,17 @@ Job *job_get(const char *id) > return job_get_locked(id); > } > > +void job_set_aio_context(Job *job, AioContext *ctx) > +{ > + /* protect against read in job_finish_sync_locked and job_start */ > + assert(qemu_in_main_thread()); > + /* protect against read in job_do_yield_locked */ > + JOB_LOCK_GUARD(); > + /* ensure the coroutine is quiescent while the AioContext is changed */ > + assert(job->pause_count > 0); > + job->aio_context = ctx; > +} > + > /* Called with job_mutex *not* held. */ > static void job_sleep_timer_cb(void *opaque) > { > @@ -1380,6 +1391,7 @@ int job_finish_sync_locked(Job *job, > { > Error *local_err = NULL; > int ret; > + assert(qemu_in_main_thread()); > > job_ref_locked(job); > Missed update of block_job_add_bdrv(), block_job_get_aio_context(). Should they have an assertion too? Also some occurences in test, but that doesn't seem significant.
Am 11/07/2022 um 16:19 schrieb Vladimir Sementsov-Ogievskiy: > On 7/6/22 23:15, Emanuele Giuseppe Esposito wrote: >> In order to make it thread safe, implement a "fake rwlock", >> where we allow reads under BQL *or* job_mutex held, but >> writes only under BQL *and* job_mutex. >> >> The only write we have is in child_job_set_aio_ctx > > also in job_create of course, but it seems safe anyway > >> , which always >> happens under drain (so the job is paused). >> For this reason, introduce job_set_aio_context and make sure that >> the context is set under BQL, job_mutex and drain. >> Also make sure all other places where the aiocontext is read >> are protected. >> >> Note: at this stage, job_{lock/unlock} and job lock guard macros >> are *nop*. >> >> Suggested-by: Paolo Bonzini <pbonzini@redhat.com> >> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> >> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> >> --- >> block/replication.c | 6 ++++-- >> blockjob.c | 3 ++- >> include/qemu/job.h | 19 ++++++++++++++++++- >> job.c | 12 ++++++++++++ >> 4 files changed, 36 insertions(+), 4 deletions(-) >> >> diff --git a/block/replication.c b/block/replication.c >> index 55c8f894aa..2189863df1 100644 >> --- a/block/replication.c >> +++ b/block/replication.c >> @@ -148,8 +148,10 @@ static void replication_close(BlockDriverState *bs) >> } >> if (s->stage == BLOCK_REPLICATION_FAILOVER) { >> commit_job = &s->commit_job->job; >> - assert(commit_job->aio_context == >> qemu_get_current_aio_context()); >> - job_cancel_sync(commit_job, false); >> + WITH_JOB_LOCK_GUARD() { >> + assert(commit_job->aio_context == >> qemu_get_current_aio_context()); >> + job_cancel_sync_locked(commit_job, false); >> + } >> } >> if (s->mode == REPLICATION_MODE_SECONDARY) { >> diff --git a/blockjob.c b/blockjob.c >> index bce05a9096..0d120ed126 100644 >> --- a/blockjob.c >> +++ b/blockjob.c >> @@ -166,12 +166,13 @@ static void child_job_set_aio_ctx(BdrvChild *c, >> AioContext *ctx, >> bdrv_set_aio_context_ignore(sibling->bs, ctx, ignore); >> } >> - job->job.aio_context = ctx; >> + job_set_aio_context(&job->job, ctx); >> } >> static AioContext *child_job_get_parent_aio_context(BdrvChild *c) >> { >> BlockJob *job = c->opaque; >> + assert(qemu_in_main_thread()); >> return job->job.aio_context; >> } >> diff --git a/include/qemu/job.h b/include/qemu/job.h >> index 5709e8d4a8..c144aabefc 100644 >> --- a/include/qemu/job.h >> +++ b/include/qemu/job.h >> @@ -77,7 +77,12 @@ typedef struct Job { >> /** Protected by AioContext lock */ >> - /** AioContext to run the job coroutine in */ >> + /** >> + * AioContext to run the job coroutine in. >> + * This field can be read when holding either the BQL (so we are in >> + * the main loop) or the job_mutex. >> + * It can be only written when we hold *both* BQL and job_mutex. >> + */ >> AioContext *aio_context; >> /** Reference count of the block job */ >> @@ -741,4 +746,16 @@ int job_finish_sync(Job *job, void (*finish)(Job >> *, Error **errp), >> int job_finish_sync_locked(Job *job, void (*finish)(Job *, Error >> **errp), >> Error **errp); >> +/** >> + * Sets the @job->aio_context. >> + * Called with job_mutex *not* held. >> + * >> + * This function must run in the main thread to protect against >> + * concurrent read in job_finish_sync_locked(), >> + * takes the job_mutex lock to protect against the read in >> + * job_do_yield_locked(), and must be called when the coroutine >> + * is quiescent. >> + */ >> +void job_set_aio_context(Job *job, AioContext *ctx); >> + >> #endif >> diff --git a/job.c b/job.c >> index 405f39566b..66cae82593 100644 >> --- a/job.c >> +++ b/job.c >> @@ -394,6 +394,17 @@ Job *job_get(const char *id) >> return job_get_locked(id); >> } >> +void job_set_aio_context(Job *job, AioContext *ctx) >> +{ >> + /* protect against read in job_finish_sync_locked and job_start */ >> + assert(qemu_in_main_thread()); >> + /* protect against read in job_do_yield_locked */ >> + JOB_LOCK_GUARD(); >> + /* ensure the coroutine is quiescent while the AioContext is >> changed */ >> + assert(job->pause_count > 0); >> + job->aio_context = ctx; >> +} >> + >> /* Called with job_mutex *not* held. */ >> static void job_sleep_timer_cb(void *opaque) >> { >> @@ -1380,6 +1391,7 @@ int job_finish_sync_locked(Job *job, >> { >> Error *local_err = NULL; >> int ret; >> + assert(qemu_in_main_thread()); >> job_ref_locked(job); >> > > > Missed update of block_job_add_bdrv(), block_job_get_aio_context(). > Should they have an assertion too? > > Also some occurences in test, but that doesn't seem significant. > Both have GLOBAL_STATE_CODE. Emanuele
diff --git a/block/replication.c b/block/replication.c index 55c8f894aa..2189863df1 100644 --- a/block/replication.c +++ b/block/replication.c @@ -148,8 +148,10 @@ static void replication_close(BlockDriverState *bs) } if (s->stage == BLOCK_REPLICATION_FAILOVER) { commit_job = &s->commit_job->job; - assert(commit_job->aio_context == qemu_get_current_aio_context()); - job_cancel_sync(commit_job, false); + WITH_JOB_LOCK_GUARD() { + assert(commit_job->aio_context == qemu_get_current_aio_context()); + job_cancel_sync_locked(commit_job, false); + } } if (s->mode == REPLICATION_MODE_SECONDARY) { diff --git a/blockjob.c b/blockjob.c index bce05a9096..0d120ed126 100644 --- a/blockjob.c +++ b/blockjob.c @@ -166,12 +166,13 @@ static void child_job_set_aio_ctx(BdrvChild *c, AioContext *ctx, bdrv_set_aio_context_ignore(sibling->bs, ctx, ignore); } - job->job.aio_context = ctx; + job_set_aio_context(&job->job, ctx); } static AioContext *child_job_get_parent_aio_context(BdrvChild *c) { BlockJob *job = c->opaque; + assert(qemu_in_main_thread()); return job->job.aio_context; } diff --git a/include/qemu/job.h b/include/qemu/job.h index 5709e8d4a8..c144aabefc 100644 --- a/include/qemu/job.h +++ b/include/qemu/job.h @@ -77,7 +77,12 @@ typedef struct Job { /** Protected by AioContext lock */ - /** AioContext to run the job coroutine in */ + /** + * AioContext to run the job coroutine in. + * This field can be read when holding either the BQL (so we are in + * the main loop) or the job_mutex. + * It can be only written when we hold *both* BQL and job_mutex. + */ AioContext *aio_context; /** Reference count of the block job */ @@ -741,4 +746,16 @@ int job_finish_sync(Job *job, void (*finish)(Job *, Error **errp), int job_finish_sync_locked(Job *job, void (*finish)(Job *, Error **errp), Error **errp); +/** + * Sets the @job->aio_context. + * Called with job_mutex *not* held. + * + * This function must run in the main thread to protect against + * concurrent read in job_finish_sync_locked(), + * takes the job_mutex lock to protect against the read in + * job_do_yield_locked(), and must be called when the coroutine + * is quiescent. + */ +void job_set_aio_context(Job *job, AioContext *ctx); + #endif diff --git a/job.c b/job.c index 405f39566b..66cae82593 100644 --- a/job.c +++ b/job.c @@ -394,6 +394,17 @@ Job *job_get(const char *id) return job_get_locked(id); } +void job_set_aio_context(Job *job, AioContext *ctx) +{ + /* protect against read in job_finish_sync_locked and job_start */ + assert(qemu_in_main_thread()); + /* protect against read in job_do_yield_locked */ + JOB_LOCK_GUARD(); + /* ensure the coroutine is quiescent while the AioContext is changed */ + assert(job->pause_count > 0); + job->aio_context = ctx; +} + /* Called with job_mutex *not* held. */ static void job_sleep_timer_cb(void *opaque) { @@ -1380,6 +1391,7 @@ int job_finish_sync_locked(Job *job, { Error *local_err = NULL; int ret; + assert(qemu_in_main_thread()); job_ref_locked(job);
In order to make it thread safe, implement a "fake rwlock", where we allow reads under BQL *or* job_mutex held, but writes only under BQL *and* job_mutex. The only write we have is in child_job_set_aio_ctx, which always happens under drain (so the job is paused). For this reason, introduce job_set_aio_context and make sure that the context is set under BQL, job_mutex and drain. Also make sure all other places where the aiocontext is read are protected. Note: at this stage, job_{lock/unlock} and job lock guard macros are *nop*. Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> --- block/replication.c | 6 ++++-- blockjob.c | 3 ++- include/qemu/job.h | 19 ++++++++++++++++++- job.c | 12 ++++++++++++ 4 files changed, 36 insertions(+), 4 deletions(-)