From: Peter Zijlstra Date: Fri, 26 Sep 2008 17:32:21 +0000 (+0200) Subject: futex: reduce mmap_sem usage X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=61270708ecf1cda148e84fbf6e0703ee5aa81814;p=linux-beck.git futex: reduce mmap_sem usage now that we rely on get_user_pages() for the shared key handling move all the mmap_sem stuff closely around the slow paths. Signed-off-by: Peter Zijlstra Acked-by: Nick Piggin Signed-off-by: Ingo Molnar --- diff --git a/kernel/futex.c b/kernel/futex.c index a4c39fa0a7a3..6a726684217e 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -122,24 +122,6 @@ struct futex_hash_bucket { static struct futex_hash_bucket futex_queues[1<mmap_sem, when futex is shared - */ -static inline void futex_lock_mm(struct rw_semaphore *fshared) -{ - if (fshared) - down_read(fshared); -} - -/* - * Release mm->mmap_sem, when the futex is shared - */ -static inline void futex_unlock_mm(struct rw_semaphore *fshared) -{ - if (fshared) - up_read(fshared); -} - /* * We hash on the keys returned from get_futex_key (see below). */ @@ -250,7 +232,9 @@ static int get_futex_key(u32 __user *uaddr, struct rw_semaphore *fshared, } again: + down_read(&mm->mmap_sem); err = get_user_pages(current, mm, address, 1, 0, 0, &page, NULL); + up_read(&mm->mmap_sem); if (err < 0) return err; @@ -327,8 +311,7 @@ static int futex_handle_fault(unsigned long address, if (attempt > 2) return ret; - if (!fshared) - down_read(&mm->mmap_sem); + down_read(&mm->mmap_sem); vma = find_vma(mm, address); if (vma && address >= vma->vm_start && (vma->vm_flags & VM_WRITE)) { @@ -348,8 +331,7 @@ static int futex_handle_fault(unsigned long address, current->min_flt++; } } - if (!fshared) - up_read(&mm->mmap_sem); + up_read(&mm->mmap_sem); return ret; } @@ -719,8 +701,6 @@ static int futex_wake(u32 __user *uaddr, struct rw_semaphore *fshared, if (!bitset) return -EINVAL; - futex_lock_mm(fshared); - ret = get_futex_key(uaddr, fshared, &key); if (unlikely(ret != 0)) goto out; @@ -749,7 +729,6 @@ static int futex_wake(u32 __user *uaddr, struct rw_semaphore *fshared, spin_unlock(&hb->lock); out: put_futex_key(fshared, &key); - futex_unlock_mm(fshared); return ret; } @@ -769,8 +748,6 @@ futex_wake_op(u32 __user *uaddr1, struct rw_semaphore *fshared, int ret, op_ret, attempt = 0; retryfull: - futex_lock_mm(fshared); - ret = get_futex_key(uaddr1, fshared, &key1); if (unlikely(ret != 0)) goto out; @@ -821,12 +798,6 @@ retry: goto retry; } - /* - * If we would have faulted, release mmap_sem, - * fault it in and start all over again. - */ - futex_unlock_mm(fshared); - ret = get_user(dummy, uaddr2); if (ret) return ret; @@ -864,7 +835,6 @@ retry: out: put_futex_key(fshared, &key2); put_futex_key(fshared, &key1); - futex_unlock_mm(fshared); return ret; } @@ -884,8 +854,6 @@ static int futex_requeue(u32 __user *uaddr1, struct rw_semaphore *fshared, int ret, drop_count = 0; retry: - futex_lock_mm(fshared); - ret = get_futex_key(uaddr1, fshared, &key1); if (unlikely(ret != 0)) goto out; @@ -908,12 +876,6 @@ static int futex_requeue(u32 __user *uaddr1, struct rw_semaphore *fshared, if (hb1 != hb2) spin_unlock(&hb2->lock); - /* - * If we would have faulted, release mmap_sem, fault - * it in and start all over again. - */ - futex_unlock_mm(fshared); - ret = get_user(curval, uaddr1); if (!ret) @@ -967,7 +929,6 @@ out_unlock: out: put_futex_key(fshared, &key2); put_futex_key(fshared, &key1); - futex_unlock_mm(fshared); return ret; } @@ -1211,8 +1172,6 @@ static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared, q.pi_state = NULL; q.bitset = bitset; retry: - futex_lock_mm(fshared); - q.key = FUTEX_KEY_INIT; ret = get_futex_key(uaddr, fshared, &q.key); if (unlikely(ret != 0)) @@ -1245,12 +1204,6 @@ static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared, if (unlikely(ret)) { queue_unlock(&q, hb); - /* - * If we would have faulted, release mmap_sem, fault it in and - * start all over again. - */ - futex_unlock_mm(fshared); - ret = get_user(uval, uaddr); if (!ret) @@ -1264,12 +1217,6 @@ static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared, /* Only actually queue if *uaddr contained val. */ queue_me(&q, hb); - /* - * Now the futex is queued and we have checked the data, we - * don't want to hold mmap_sem while we sleep. - */ - futex_unlock_mm(fshared); - /* * There might have been scheduling since the queue_me(), as we * cannot hold a spinlock across the get_user() in case it @@ -1355,7 +1302,6 @@ static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared, out_release_sem: put_futex_key(fshared, &q.key); - futex_unlock_mm(fshared); return ret; } @@ -1404,8 +1350,6 @@ static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared, q.pi_state = NULL; retry: - futex_lock_mm(fshared); - q.key = FUTEX_KEY_INIT; ret = get_futex_key(uaddr, fshared, &q.key); if (unlikely(ret != 0)) @@ -1495,7 +1439,6 @@ static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared, * exit to complete. */ queue_unlock(&q, hb); - futex_unlock_mm(fshared); cond_resched(); goto retry; @@ -1527,12 +1470,6 @@ static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared, */ queue_me(&q, hb); - /* - * Now the futex is queued and we have checked the data, we - * don't want to hold mmap_sem while we sleep. - */ - futex_unlock_mm(fshared); - WARN_ON(!q.pi_state); /* * Block on the PI mutex: @@ -1545,7 +1482,6 @@ static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared, ret = ret ? 0 : -EWOULDBLOCK; } - futex_lock_mm(fshared); spin_lock(q.lock_ptr); if (!ret) { @@ -1611,7 +1547,6 @@ static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared, /* Unqueue and drop the lock */ unqueue_me_pi(&q); - futex_unlock_mm(fshared); if (to) destroy_hrtimer_on_stack(&to->timer); @@ -1622,7 +1557,6 @@ static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared, out_release_sem: put_futex_key(fshared, &q.key); - futex_unlock_mm(fshared); if (to) destroy_hrtimer_on_stack(&to->timer); return ret; @@ -1646,8 +1580,6 @@ static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared, goto retry_unlocked; } - futex_unlock_mm(fshared); - ret = get_user(uval, uaddr); if (!ret && (uval != -EFAULT)) goto retry; @@ -1679,10 +1611,6 @@ retry: */ if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current)) return -EPERM; - /* - * First take all the futex related locks: - */ - futex_lock_mm(fshared); ret = get_futex_key(uaddr, fshared, &key); if (unlikely(ret != 0)) @@ -1742,7 +1670,6 @@ out_unlock: spin_unlock(&hb->lock); out: put_futex_key(fshared, &key); - futex_unlock_mm(fshared); return ret; @@ -1766,8 +1693,6 @@ pi_faulted: goto retry_unlocked; } - futex_unlock_mm(fshared); - ret = get_user(uval, uaddr); if (!ret && (uval != -EFAULT)) goto retry;