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dkim=pass header.d=oracle.com header.s=corp-2021-07-09 header.b=MU68LcvT; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b="Zb77Ind/"; spf=none (imf04.hostedemail.com: domain of daniel.m.jordan@oracle.com has no SPF policy when checking 205.220.165.32) smtp.mailfrom=daniel.m.jordan@oracle.com; dmarc=pass (policy=none) header.from=oracle.com X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 636234000C X-Stat-Signature: o9usgnpczjiiygjtwq6pwat5h86ocj4c X-HE-Tag: 1641430065-378890 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: A caller of padata_do_multithreaded() can unwittingly introduce deadlocks if it already holds lock(s) that thread_fn() takes. Lockdep can't detect such a dependency because it doesn't know that padata_do_multithreaded() waits on the helper threads. Use a lockdep_map to encode the dependency, following the pattern in workqueue, CPU hotplug, and other parts of the kernel. See commit 4e6045f13478 ("workqueue: debug flushing deadlocks with lockdep") for an example of a similar situation. Each padata_do_multithreaded() callsite gets its own lock_class_key to avoid false positives involving locks from different calls that don't depend on each other. Signed-off-by: Daniel Jordan Suggested-by: Peter Zijlstra --- include/linux/padata.h | 22 +++++++++++++++++++++- kernel/padata.c | 15 +++++++++++++-- 2 files changed, 34 insertions(+), 3 deletions(-) diff --git a/include/linux/padata.h b/include/linux/padata.h index 2a9fa459463d..907d624a8ca4 100644 --- a/include/linux/padata.h +++ b/include/linux/padata.h @@ -17,6 +17,7 @@ #include #include #include +#include #define PADATA_CPU_SERIAL 0x01 #define PADATA_CPU_PARALLEL 0x02 @@ -188,6 +189,23 @@ extern void __init padata_init(void); static inline void __init padata_init(void) {} #endif +#ifdef CONFIG_LOCKDEP + +#define padata_do_multithreaded(job) \ +({ \ + static struct lock_class_key __key; \ + const char *__map_name = "padata master waiting"; \ + \ + padata_do_multithreaded_job((job), &__key, __map_name); \ +}) + +#else + +#define padata_do_multithreaded(job) \ + padata_do_multithreaded_job((job), NULL, NULL) + +#endif + extern struct padata_instance *padata_alloc(const char *name); extern void padata_free(struct padata_instance *pinst); extern struct padata_shell *padata_alloc_shell(struct padata_instance *pinst); @@ -195,7 +213,9 @@ extern void padata_free_shell(struct padata_shell *ps); extern int padata_do_parallel(struct padata_shell *ps, struct padata_priv *padata, int *cb_cpu); extern void padata_do_serial(struct padata_priv *padata); -extern int padata_do_multithreaded(struct padata_mt_job *job); +extern int padata_do_multithreaded_job(struct padata_mt_job *job, + struct lock_class_key *key, + const char *map_name); extern int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type, cpumask_var_t cpumask); #endif diff --git a/kernel/padata.c b/kernel/padata.c index d0876f861464..b458deb17121 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -64,6 +64,9 @@ struct padata_mt_job_state { unsigned long position; unsigned long remaining_size; struct list_head failed_works; +#ifdef CONFIG_LOCKDEP + struct lockdep_map lockdep_map; +#endif }; static void padata_free_pd(struct parallel_data *pd); @@ -470,9 +473,11 @@ static void padata_mt_helper(struct work_struct *w) ps->remaining_size -= size; spin_unlock(&ps->lock); + lock_map_acquire(&ps->lockdep_map); ret = job->thread_fn(position, end, job->fn_arg); + lock_map_release(&ps->lockdep_map); spin_lock(&ps->lock); if (ret) { @@ -552,14 +557,16 @@ static void padata_undo(struct padata_mt_job_state *ps, } /** - * padata_do_multithreaded - run a multithreaded job + * padata_do_multithreaded_job - run a multithreaded job * @job: Description of the job. * * See the definition of struct padata_mt_job for more details. * * Return: 0 or a client-specific nonzero error code. */ -int padata_do_multithreaded(struct padata_mt_job *job) +int padata_do_multithreaded_job(struct padata_mt_job *job, + struct lock_class_key *key, + const char *map_name) { /* In case threads finish at different times. */ static const unsigned long load_balance_factor = 4; @@ -583,6 +590,7 @@ int padata_do_multithreaded(struct padata_mt_job *job) spin_lock_init(&ps.lock); init_completion(&ps.completion); + lockdep_init_map(&ps.lockdep_map, map_name, key, 0); INIT_LIST_HEAD(&ps.failed_works); ps.job = job; ps.nworks = padata_work_alloc_mt(nworks, &ps, &works); @@ -601,6 +609,9 @@ int padata_do_multithreaded(struct padata_mt_job *job) ps.chunk_size = max(ps.chunk_size, job->min_chunk); ps.chunk_size = roundup(ps.chunk_size, job->align); + lock_map_acquire(&ps.lockdep_map); + lock_map_release(&ps.lockdep_map); + list_for_each_entry(pw, &works, pw_list) queue_work(system_unbound_wq, &pw->pw_work);