From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-x72e.google.com (mail-qk1-x72e.google.com [IPv6:2607:f8b0:4864:20::72e]) by sourceware.org (Postfix) with ESMTPS id 0AB54384BC30 for ; Thu, 15 Apr 2021 19:52:19 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 0AB54384BC30 Received: by mail-qk1-x72e.google.com with SMTP id b139so21119467qkc.10 for ; Thu, 15 Apr 2021 12:52:19 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=2C/HvXN8LI6iM7LOpX2YLEFp7bpzdwSF5nxYZTFywbc=; b=lfEb1q8roauvYSvq1cYtF5GL4g76FN98Z7r/Cahxq2clxKy6SOeLOVe4PAQ2aNCvt+ tqRVrErsKeMGkcOXdzI71MmelY1DAPztIm7Rk4X2sZFeGr7nJnA9F801x5/4sSq5y9cl 2qK5WpYd24+tmhJcypkynJzxBAhBK+rwq6vWMdd7Mz/y4XqOdhujqw9lN985KHVulr6n jfQ7Scr7NGlaKfEVVtdG96Er7MBMTNfqECe4RooOiQTux5YGYY0MT63KgqjvSz70WbaO WD/YldgH83xFF9p3OnQSPq8JSmCMoQcsT888QyvwDvI2AtP1KaswntV9eADoL/ZCG/AR 9f8Q== X-Gm-Message-State: AOAM533FCpIY1P4K1VkmDTtJz6/+esKw3FZjTAo4H2ejIW/+xSFvt8lQ SMBfNEgzmCYTVtYNi0nTt3cJMAq9RPugmmC+ X-Google-Smtp-Source: ABdhPJxC1OJYG0VgS/BXqEsA/gZnmm/wBHCb5ZEKUzX7wFR4Dn4HOSa6dkTtfooxqfA8T/V69X09xQ== X-Received: by 2002:a37:84c6:: with SMTP id g189mr1774645qkd.154.1618516338282; Thu, 15 Apr 2021 12:52:18 -0700 (PDT) Received: from [192.168.1.132] ([177.194.41.149]) by smtp.gmail.com with ESMTPSA id a19sm2546186qtn.41.2021.04.15.12.52.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 15 Apr 2021 12:52:18 -0700 (PDT) Subject: Re: [PATCH v2 13/14] elf: Remove lazy tlsdesc relocation related code To: libc-alpha@sourceware.org, Szabolcs Nagy References: From: Adhemerval Zanella Message-ID: <2c05d53b-1c61-ee5c-2f0f-3f05ecf7fc2d@linaro.org> Date: Thu, 15 Apr 2021 16:52:15 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-12.6 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 15 Apr 2021 19:52:20 -0000 On 13/04/2021 05:21, Szabolcs Nagy via Libc-alpha wrote: > Remove generic tlsdesc code related to lazy tlsdesc processing since > lazy tlsdesc relocation is no longer supported. This includes removing > GL(dl_load_lock) from _dl_make_tlsdesc_dynamic which is only called at > load time when that lock is already held. > > Added a documentation comment too. LGTM, thanks. Reviewed-by: Adhemerval Zanella > --- > elf/tlsdeschtab.h | 53 +++++---------------------------------- > sysdeps/aarch64/tlsdesc.c | 1 - > sysdeps/arm/tlsdesc.c | 1 - > sysdeps/i386/tlsdesc.c | 1 - > sysdeps/x86_64/tlsdesc.c | 1 - > 5 files changed, 6 insertions(+), 51 deletions(-) > > diff --git a/elf/tlsdeschtab.h b/elf/tlsdeschtab.h > index 21695fd1e9..85bd0415e1 100644 > --- a/elf/tlsdeschtab.h > +++ b/elf/tlsdeschtab.h > @@ -78,6 +78,10 @@ map_generation (struct link_map *map) > return GL(dl_tls_generation) + 1; > } > > +/* Returns the data pointer for a given map and tls offset that is used > + to fill in one of the GOT entries referenced by a TLSDESC relocation > + when using dynamic TLS. This requires allocation, returns NULL on > + allocation failure. */ > void * > _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset) > { > @@ -85,18 +89,12 @@ _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset) > void **entry; > struct tlsdesc_dynamic_arg *td, test; > > - /* FIXME: We could use a per-map lock here, but is it worth it? */ > - __rtld_lock_lock_recursive (GL(dl_load_lock)); > - > ht = map->l_mach.tlsdesc_table; > if (! ht) > { > ht = htab_create (); > if (! ht) > - { > - __rtld_lock_unlock_recursive (GL(dl_load_lock)); > - return 0; > - } > + return 0; > map->l_mach.tlsdesc_table = ht; > } > Ok. > @@ -104,15 +102,11 @@ _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset) > test.tlsinfo.ti_offset = ti_offset; > entry = htab_find_slot (ht, &test, 1, hash_tlsdesc, eq_tlsdesc); > if (! entry) > - { > - __rtld_lock_unlock_recursive (GL(dl_load_lock)); > - return 0; > - } > + return 0; > > if (*entry) > { > td = *entry; > - __rtld_lock_unlock_recursive (GL(dl_load_lock)); > return td; > } > Ok. > @@ -122,44 +116,9 @@ _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset) > thread. */ > td->gen_count = map_generation (map); > td->tlsinfo = test.tlsinfo; > - > - __rtld_lock_unlock_recursive (GL(dl_load_lock)); > return td; > } > > # endif /* SHARED */ > > -/* The idea of the following two functions is to stop multiple threads > - from attempting to resolve the same TLS descriptor without busy > - waiting. Ideally, we should be able to release the lock right > - after changing td->entry, and then using say a condition variable > - or a futex wake to wake up any waiting threads, but let's try to > - avoid introducing such dependencies. */ > - > -static int > -__attribute__ ((unused)) > -_dl_tlsdesc_resolve_early_return_p (struct tlsdesc volatile *td, void *caller) > -{ > - if (caller != atomic_load_relaxed (&td->entry)) > - return 1; > - > - __rtld_lock_lock_recursive (GL(dl_load_lock)); > - if (caller != atomic_load_relaxed (&td->entry)) > - { > - __rtld_lock_unlock_recursive (GL(dl_load_lock)); > - return 1; > - } > - > - atomic_store_relaxed (&td->entry, _dl_tlsdesc_resolve_hold); > - > - return 0; > -} > - > -static void > -__attribute__ ((unused)) > -_dl_tlsdesc_wake_up_held_fixups (void) > -{ > - __rtld_lock_unlock_recursive (GL(dl_load_lock)); > -} > - > #endif Ok. > diff --git a/sysdeps/aarch64/tlsdesc.c b/sysdeps/aarch64/tlsdesc.c > index 9b6a8b0ec4..3c1bcd8fe6 100644 > --- a/sysdeps/aarch64/tlsdesc.c > +++ b/sysdeps/aarch64/tlsdesc.c > @@ -22,7 +22,6 @@ > #include > #include > #include > -#define _dl_tlsdesc_resolve_hold 0 > #include > > /* Unmap the dynamic object, but also release its TLS descriptor table Ok. > diff --git a/sysdeps/arm/tlsdesc.c b/sysdeps/arm/tlsdesc.c > index 2f70adef5c..b3d1735af4 100644 > --- a/sysdeps/arm/tlsdesc.c > +++ b/sysdeps/arm/tlsdesc.c > @@ -20,7 +20,6 @@ > #include > #include > #include > -#define _dl_tlsdesc_resolve_hold 0 > #include > > /* Unmap the dynamic object, but also release its TLS descriptor table Ok. > diff --git a/sysdeps/i386/tlsdesc.c b/sysdeps/i386/tlsdesc.c > index 436a21f66b..364c7769ce 100644 > --- a/sysdeps/i386/tlsdesc.c > +++ b/sysdeps/i386/tlsdesc.c > @@ -20,7 +20,6 @@ > #include > #include > #include > -#define _dl_tlsdesc_resolve_hold 0 > #include > > /* Unmap the dynamic object, but also release its TLS descriptor table Ok. > diff --git a/sysdeps/x86_64/tlsdesc.c b/sysdeps/x86_64/tlsdesc.c > index ecf864d6ee..3bb80517a3 100644 > --- a/sysdeps/x86_64/tlsdesc.c > +++ b/sysdeps/x86_64/tlsdesc.c > @@ -20,7 +20,6 @@ > #include > #include > #include > -#define _dl_tlsdesc_resolve_hold 0 > #include > > /* Unmap the dynamic object, but also release its TLS descriptor table > Ok.