From e75b16cf93ebbc1ce758d3ea6b2923e8b2457c68 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Thu, 19 Jun 2014 02:16:57 -0400 Subject: [PATCH] change dynamic TLS installation strategy to optimize access previously, accesses to dynamic TLS had to check two conditions before being able to use a dtv slot: (1) that the module index was within the bounds of the current dtv size, and (2) that the dynamic tls for the requested module index was already installed in the dtv. this commit changes the installation strategy so that, whenever an attempt is made to access dynamic TLS that's not yet installed in the dtv, the dynamic TLS for all lower-index modules is also installed. thus it provides a new invariant: if a given module index is within the bounds of the current dtv size, we automatically know that its TLS is installed and directly available. the requirement that the second condition (above) be checked is eliminated. --- src/ldso/dynlink.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c index 66bca506..2b6f0c94 100644 --- a/src/ldso/dynlink.c +++ b/src/ldso/dynlink.c @@ -1034,13 +1034,13 @@ void *__copy_tls(unsigned char *mem) void *__tls_get_addr(size_t *v) { pthread_t self = __pthread_self(); - if (v[0]<=(size_t)self->dtv[0] && self->dtv[v[0]]) + if (v[0]<=(size_t)self->dtv[0]) return (char *)self->dtv[v[0]]+v[1]; /* Block signals to make accessing new TLS async-signal-safe */ sigset_t set; pthread_sigmask(SIG_BLOCK, SIGALL_SET, &set); - if (v[0]<=(size_t)self->dtv[0] && self->dtv[v[0]]) { + if (v[0]<=(size_t)self->dtv[0]) { pthread_sigmask(SIG_SETMASK, &set, 0); return (char *)self->dtv[v[0]]+v[1]; } @@ -1062,12 +1062,18 @@ void *__tls_get_addr(size_t *v) self->dtv = newdtv; } - /* Get new TLS memory from new DSO */ - unsigned char *mem = p->new_tls + - (p->tls_size + p->tls_align) * a_fetch_add(&p->new_tls_idx,1); - mem += ((uintptr_t)p->tls_image - (uintptr_t)mem) & (p->tls_align-1); - self->dtv[v[0]] = mem; - memcpy(mem, p->tls_image, p->tls_len); + /* Get new TLS memory from all new DSOs up to the requested one */ + unsigned char *mem; + for (p=head; ; p=p->next) { + if (!p->tls_id || self->dtv[p->tls_id]) continue; + mem = p->new_tls + (p->tls_size + p->tls_align) + * a_fetch_add(&p->new_tls_idx,1); + mem += ((uintptr_t)p->tls_image - (uintptr_t)mem) + & (p->tls_align-1); + self->dtv[p->tls_id] = mem; + memcpy(mem, p->tls_image, p->tls_len); + if (p->tls_id == v[0]) break; + } pthread_sigmask(SIG_SETMASK, &set, 0); return mem + v[1]; } -- 2.25.1