linux-kernel - Re: [PATCH v3 03/22] perf dso: Make lock error check and add BUG

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Date:   Fri, 11 Feb 2022 14:13:46 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Darren Hart <dvhart@...radead.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        André Almeida <andrealmeid@...labora.com>,
        James Clark <james.clark@....com>,
        John Garry <john.garry@...wei.com>,
        Riccardo Mancini <rickyman7@...il.com>,
        Yury Norov <yury.norov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Leo Yan <leo.yan@...aro.org>, Andi Kleen <ak@...ux.intel.com>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Shunsuke Nakamura <nakamura.shun@...itsu.com>,
        Song Liu <song@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Miaoqian Lin <linmq006@...il.com>,
        Stephen Brennan <stephen.s.brennan@...cle.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        Alexey Bayduraev <alexey.v.bayduraev@...ux.intel.com>,
        German Gomez <german.gomez@....com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Eric Dumazet <edumazet@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Hao Luo <haoluo@...gle.com>, eranian@...gle.com
Subject: Re: [PATCH v3 03/22] perf dso: Make lock error check and add BUG_ONs

Em Fri, Feb 11, 2022 at 02:33:56AM -0800, Ian Rogers escreveu:
> Make the pthread mutex on dso use the error check type. This allows
> deadlock checking via the return type. Assert the returned value from
> mutex lock is always 0.

I think this is too blunt/pervasive source code wise, perhaps we should
wrap this like its done with rwsem in tools/perf/util/rwsem.h to get
away from pthreads primitives and make the source code look more like
a kernel one and then, taking advantage of the so far ideologic
needless indirection, add this BUG_ON if we build with "DEBUG=1" or
something, wdyt?

- Arnaldo
 
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/util/dso.c    | 12 +++++++++---
>  tools/perf/util/symbol.c |  2 +-
>  2 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
> index 9cc8a1772b4b..6beccffeef7b 100644
> --- a/tools/perf/util/dso.c
> +++ b/tools/perf/util/dso.c
> @@ -784,7 +784,7 @@ dso_cache__free(struct dso *dso)
>  	struct rb_root *root = &dso->data.cache;
>  	struct rb_node *next = rb_first(root);
>  
> -	pthread_mutex_lock(&dso->lock);
> +	BUG_ON(pthread_mutex_lock(&dso->lock) != 0);
>  	while (next) {
>  		struct dso_cache *cache;
>  
> @@ -830,7 +830,7 @@ dso_cache__insert(struct dso *dso, struct dso_cache *new)
>  	struct dso_cache *cache;
>  	u64 offset = new->offset;
>  
> -	pthread_mutex_lock(&dso->lock);
> +	BUG_ON(pthread_mutex_lock(&dso->lock) != 0);
>  	while (*p != NULL) {
>  		u64 end;
>  
> @@ -1259,6 +1259,8 @@ struct dso *dso__new_id(const char *name, struct dso_id *id)
>  	struct dso *dso = calloc(1, sizeof(*dso) + strlen(name) + 1);
>  
>  	if (dso != NULL) {
> +		pthread_mutexattr_t lock_attr;
> +
>  		strcpy(dso->name, name);
>  		if (id)
>  			dso->id = *id;
> @@ -1286,8 +1288,12 @@ struct dso *dso__new_id(const char *name, struct dso_id *id)
>  		dso->root = NULL;
>  		INIT_LIST_HEAD(&dso->node);
>  		INIT_LIST_HEAD(&dso->data.open_entry);
> -		pthread_mutex_init(&dso->lock, NULL);
> +		pthread_mutexattr_init(&lock_attr);
> +		pthread_mutexattr_settype(&lock_attr, PTHREAD_MUTEX_ERRORCHECK);
> +		pthread_mutex_init(&dso->lock, &lock_attr);
> +		pthread_mutexattr_destroy(&lock_attr);
>  		refcount_set(&dso->refcnt, 1);
> +
>  	}
>  
>  	return dso;
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index b2ed3140a1fa..43f47532696f 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -1783,7 +1783,7 @@ int dso__load(struct dso *dso, struct map *map)
>  	}
>  
>  	nsinfo__mountns_enter(dso->nsinfo, &nsc);
> -	pthread_mutex_lock(&dso->lock);
> +	BUG_ON(pthread_mutex_lock(&dso->lock) != 0);
>  
>  	/* check again under the dso->lock */
>  	if (dso__loaded(dso)) {
> -- 
> 2.35.1.265.g69c8d7142f-goog

-- 

- Arnaldo