diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Makefile | 4 | ||||
| -rw-r--r-- | lib/iovec.c | 53 | ||||
| -rw-r--r-- | lib/klist.c | 2 | ||||
| -rw-r--r-- | lib/mpi/longlong.h | 5 | ||||
| -rw-r--r-- | lib/percpu-refcount.c | 158 |
5 files changed, 217 insertions, 5 deletions
diff --git a/lib/Makefile b/lib/Makefile index e9c52e1b853a..386db4bbc265 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -13,7 +13,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \ sha1.o md5.o irq_regs.o reciprocal_div.o argv_split.o \ proportions.o flex_proportions.o prio_heap.o ratelimit.o show_mem.o \ is_single_threaded.o plist.o decompress.o kobject_uevent.o \ - earlycpio.o + earlycpio.o percpu-refcount.o obj-$(CONFIG_ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS) += usercopy.o lib-$(CONFIG_MMU) += ioremap.o @@ -23,7 +23,7 @@ lib-y += kobject.o klist.o obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \ bust_spinlocks.o hexdump.o kasprintf.o bitmap.o scatterlist.o \ - gcd.o lcm.o list_sort.o uuid.o flex_array.o \ + gcd.o lcm.o list_sort.o uuid.o flex_array.o iovec.o \ bsearch.o find_last_bit.o find_next_bit.o llist.o memweight.o kfifo.o obj-y += string_helpers.o obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o diff --git a/lib/iovec.c b/lib/iovec.c new file mode 100644 index 000000000000..454baa88bf27 --- /dev/null +++ b/lib/iovec.c @@ -0,0 +1,53 @@ +#include <linux/uaccess.h> +#include <linux/export.h> +#include <linux/uio.h> + +/* + * Copy iovec to kernel. Returns -EFAULT on error. + * + * Note: this modifies the original iovec. + */ + +int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len) +{ + while (len > 0) { + if (iov->iov_len) { + int copy = min_t(unsigned int, len, iov->iov_len); + if (copy_from_user(kdata, iov->iov_base, copy)) + return -EFAULT; + len -= copy; + kdata += copy; + iov->iov_base += copy; + iov->iov_len -= copy; + } + iov++; + } + + return 0; +} +EXPORT_SYMBOL(memcpy_fromiovec); + +/* + * Copy kernel to iovec. Returns -EFAULT on error. + * + * Note: this modifies the original iovec. + */ + +int memcpy_toiovec(struct iovec *iov, unsigned char *kdata, int len) +{ + while (len > 0) { + if (iov->iov_len) { + int copy = min_t(unsigned int, iov->iov_len, len); + if (copy_to_user(iov->iov_base, kdata, copy)) + return -EFAULT; + kdata += copy; + len -= copy; + iov->iov_len -= copy; + iov->iov_base += copy; + } + iov++; + } + + return 0; +} +EXPORT_SYMBOL(memcpy_toiovec); diff --git a/lib/klist.c b/lib/klist.c index 0874e41609a6..358a368a2947 100644 --- a/lib/klist.c +++ b/lib/klist.c @@ -193,10 +193,10 @@ static void klist_release(struct kref *kref) if (waiter->node != n) continue; + list_del(&waiter->list); waiter->woken = 1; mb(); wake_up_process(waiter->process); - list_del(&waiter->list); } spin_unlock(&klist_remove_lock); knode_set_klist(n, NULL); diff --git a/lib/mpi/longlong.h b/lib/mpi/longlong.h index 095ab157a521..d411355f238e 100644 --- a/lib/mpi/longlong.h +++ b/lib/mpi/longlong.h @@ -318,7 +318,8 @@ extern UDItype __udiv_qrnnd(); "rM" ((USItype)(bh)), \ "rM" ((USItype)(al)), \ "rM" ((USItype)(bl))) -#if defined(_PA_RISC1_1) +#if 0 && defined(_PA_RISC1_1) +/* xmpyu uses floating point register which is not allowed in Linux kernel. */ #define umul_ppmm(wh, wl, u, v) \ do { \ union {UDItype __ll; \ @@ -337,7 +338,7 @@ do { \ #define UMUL_TIME 40 #define UDIV_TIME 80 #endif -#ifndef LONGLONG_STANDALONE +#if 0 /* #ifndef LONGLONG_STANDALONE */ #define udiv_qrnnd(q, r, n1, n0, d) \ do { USItype __r; \ (q) = __udiv_qrnnd(&__r, (n1), (n0), (d)); \ diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c new file mode 100644 index 000000000000..8bf9e719cca0 --- /dev/null +++ b/lib/percpu-refcount.c @@ -0,0 +1,158 @@ +#define pr_fmt(fmt) "%s: " fmt "\n", __func__ + +#include <linux/kernel.h> +#include <linux/percpu-refcount.h> + +/* + * Initially, a percpu refcount is just a set of percpu counters. Initially, we + * don't try to detect the ref hitting 0 - which means that get/put can just + * increment or decrement the local counter. Note that the counter on a + * particular cpu can (and will) wrap - this is fine, when we go to shutdown the + * percpu counters will all sum to the correct value + * + * (More precisely: because moduler arithmatic is commutative the sum of all the + * pcpu_count vars will be equal to what it would have been if all the gets and + * puts were done to a single integer, even if some of the percpu integers + * overflow or underflow). + * + * The real trick to implementing percpu refcounts is shutdown. We can't detect + * the ref hitting 0 on every put - this would require global synchronization + * and defeat the whole purpose of using percpu refs. + * + * What we do is require the user to keep track of the initial refcount; we know + * the ref can't hit 0 before the user drops the initial ref, so as long as we + * convert to non percpu mode before the initial ref is dropped everything + * works. + * + * Converting to non percpu mode is done with some RCUish stuff in + * percpu_ref_kill. Additionally, we need a bias value so that the atomic_t + * can't hit 0 before we've added up all the percpu refs. + */ + +#define PCPU_COUNT_BIAS (1U << 31) + +/** + * percpu_ref_init - initialize a percpu refcount + * @ref: percpu_ref to initialize + * @release: function which will be called when refcount hits 0 + * + * Initializes the refcount in single atomic counter mode with a refcount of 1; + * analagous to atomic_set(ref, 1). + * + * Note that @release must not sleep - it may potentially be called from RCU + * callback context by percpu_ref_kill(). + */ +int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release) +{ + atomic_set(&ref->count, 1 + PCPU_COUNT_BIAS); + + ref->pcpu_count = alloc_percpu(unsigned); + if (!ref->pcpu_count) + return -ENOMEM; + + ref->release = release; + return 0; +} + +/** + * percpu_ref_cancel_init - cancel percpu_ref_init() + * @ref: percpu_ref to cancel init for + * + * Once a percpu_ref is initialized, its destruction is initiated by + * percpu_ref_kill() and completes asynchronously, which can be painful to + * do when destroying a half-constructed object in init failure path. + * + * This function destroys @ref without invoking @ref->release and the + * memory area containing it can be freed immediately on return. To + * prevent accidental misuse, it's required that @ref has finished + * percpu_ref_init(), whether successful or not, but never used. + * + * The weird name and usage restriction are to prevent people from using + * this function by mistake for normal shutdown instead of + * percpu_ref_kill(). + */ +void percpu_ref_cancel_init(struct percpu_ref *ref) +{ + unsigned __percpu *pcpu_count = ref->pcpu_count; + int cpu; + + WARN_ON_ONCE(atomic_read(&ref->count) != 1 + PCPU_COUNT_BIAS); + + if (pcpu_count) { + for_each_possible_cpu(cpu) + WARN_ON_ONCE(*per_cpu_ptr(pcpu_count, cpu)); + free_percpu(ref->pcpu_count); + } +} + +static void percpu_ref_kill_rcu(struct rcu_head *rcu) +{ + struct percpu_ref *ref = container_of(rcu, struct percpu_ref, rcu); + unsigned __percpu *pcpu_count = ref->pcpu_count; + unsigned count = 0; + int cpu; + + /* Mask out PCPU_REF_DEAD */ + pcpu_count = (unsigned __percpu *) + (((unsigned long) pcpu_count) & ~PCPU_STATUS_MASK); + + for_each_possible_cpu(cpu) + count += *per_cpu_ptr(pcpu_count, cpu); + + free_percpu(pcpu_count); + + pr_debug("global %i pcpu %i", atomic_read(&ref->count), (int) count); + + /* + * It's crucial that we sum the percpu counters _before_ adding the sum + * to &ref->count; since gets could be happening on one cpu while puts + * happen on another, adding a single cpu's count could cause + * @ref->count to hit 0 before we've got a consistent value - but the + * sum of all the counts will be consistent and correct. + * + * Subtracting the bias value then has to happen _after_ adding count to + * &ref->count; we need the bias value to prevent &ref->count from + * reaching 0 before we add the percpu counts. But doing it at the same + * time is equivalent and saves us atomic operations: + */ + + atomic_add((int) count - PCPU_COUNT_BIAS, &ref->count); + + /* @ref is viewed as dead on all CPUs, send out kill confirmation */ + if (ref->confirm_kill) + ref->confirm_kill(ref); + + /* + * Now we're in single atomic_t mode with a consistent refcount, so it's + * safe to drop our initial ref: + */ + percpu_ref_put(ref); +} + +/** + * percpu_ref_kill_and_confirm - drop the initial ref and schedule confirmation + * @ref: percpu_ref to kill + * @confirm_kill: optional confirmation callback + * + * Equivalent to percpu_ref_kill() but also schedules kill confirmation if + * @confirm_kill is not NULL. @confirm_kill, which may not block, will be + * called after @ref is seen as dead from all CPUs - all further + * invocations of percpu_ref_tryget() will fail. See percpu_ref_tryget() + * for more details. + * + * Due to the way percpu_ref is implemented, @confirm_kill will be called + * after at least one full RCU grace period has passed but this is an + * implementation detail and callers must not depend on it. + */ +void percpu_ref_kill_and_confirm(struct percpu_ref *ref, + percpu_ref_func_t *confirm_kill) +{ + WARN_ONCE(REF_STATUS(ref->pcpu_count) == PCPU_REF_DEAD, + "percpu_ref_kill() called more than once!\n"); + + ref->pcpu_count = (unsigned __percpu *) + (((unsigned long) ref->pcpu_count)|PCPU_REF_DEAD); + ref->confirm_kill = confirm_kill; + + call_rcu(&ref->rcu, percpu_ref_kill_rcu); +} |