am fb0a3622: Merge "Cache getpid."

* commit 'fb0a3622f79bb0a31dd4d0e2f9cea990075ef129':
  Cache getpid.

benchmarks/unistd_benchmark.cpp

@@ -30,6 +30,17 @@ static void BM_unistd_getpid(int iters) {
 }
 BENCHMARK(BM_unistd_getpid);
 
+static void BM_unistd_getpid_syscall(int iters) {
+  StartBenchmarkTiming();
+
+  for (int i = 0; i < iters; ++i) {
+    syscall(__NR_getpid);
+  }
+
+  StopBenchmarkTiming();
+}
+BENCHMARK(BM_unistd_getpid_syscall);
+
 // Stop GCC optimizing out our pure function.
 /* Must not be static! */ pid_t (*gettid_fp)() = gettid;
 

libc/Android.mk

@@ -127,6 +127,7 @@ libc_bionic_src_files := \
     bionic/getauxval.cpp \
     bionic/getcwd.cpp \
     bionic/getpgrp.cpp \
+    bionic/getpid.cpp \
     bionic/gettid.cpp \
     bionic/inotify_init.cpp \
     bionic/lchown.cpp \

libc/SYSCALLS.TXT

@@ -97,7 +97,7 @@ ssize_t     pread64|pread(int, void*, size_t, off_t) arm64,mips64,x86_64
 ssize_t     pwrite64(int, void*, size_t, off64_t) arm,mips,x86
 ssize_t     pwrite64|pwrite(int, void*, size_t, off_t) arm64,mips64,x86_64
 int         close(int)                      all
-pid_t       getpid()    all
+pid_t       __getpid:getpid()  all
 int         munmap(void*, size_t)  all
 void*       mremap(void*, size_t, size_t, unsigned long)  all
 int         msync(const void*, size_t, int)    all

libc/arch-arm/syscalls/__getpid.S

@@ -2,7 +2,7 @@
 
 #include <private/bionic_asm.h>
 
-ENTRY(getpid)
+ENTRY(__getpid)
     mov     ip, r7
     ldr     r7, =__NR_getpid
     swi     #0
@@ -11,4 +11,4 @@ ENTRY(getpid)
     bxls    lr
     neg     r0, r0
     b       __set_errno
-END(getpid)
+END(__getpid)

libc/arch-arm64/syscalls/__getpid.S

@@ -2,7 +2,7 @@
 
 #include <private/bionic_asm.h>
 
-ENTRY(getpid)
+ENTRY(__getpid)
     mov     x8, __NR_getpid
     svc     #0
 
@@ -11,4 +11,5 @@ ENTRY(getpid)
     b.hi    __set_errno
 
     ret
-END(getpid)
+END(__getpid)
+.hidden __getpid

libc/arch-mips/syscalls/__getpid.S

@@ -2,7 +2,7 @@
 
 #include <private/bionic_asm.h>
 
-ENTRY(getpid)
+ENTRY(__getpid)
     .set noreorder
     .cpload t9
     li v0, __NR_getpid
@@ -16,4 +16,4 @@ ENTRY(getpid)
     j t9
     nop
     .set reorder
-END(getpid)
+END(__getpid)

libc/arch-mips64/syscalls/__getpid.S

@@ -2,7 +2,7 @@
 
 #include <private/bionic_asm.h>
 
-ENTRY(getpid)
+ENTRY(__getpid)
     .set push
     .set noreorder
     li v0, __NR_getpid
@@ -22,4 +22,5 @@ ENTRY(getpid)
     j t9
     move ra, t0
     .set pop
-END(getpid)
+END(__getpid)
+.hidden __getpid

libc/arch-x86/syscalls/__getpid.S

@@ -2,7 +2,7 @@
 
 #include <private/bionic_asm.h>
 
-ENTRY(getpid)
+ENTRY(__getpid)
     movl    $__NR_getpid, %eax
     int     $0x80
     cmpl    $-MAX_ERRNO, %eax
@@ -13,4 +13,4 @@ ENTRY(getpid)
     addl    $4, %esp
 1:
     ret
-END(getpid)
+END(__getpid)

libc/arch-x86_64/syscalls/__getpid.S

@@ -2,7 +2,7 @@
 
 #include <private/bionic_asm.h>
 
-ENTRY(getpid)
+ENTRY(__getpid)
     movl    $__NR_getpid, %eax
     syscall
     cmpq    $-MAX_ERRNO, %rax
@@ -12,4 +12,5 @@ ENTRY(getpid)
     call    __set_errno
 1:
     ret
-END(getpid)
+END(__getpid)
+.hidden __getpid

libc/bionic/fork.cpp

@@ -31,19 +31,26 @@
 
 #include "pthread_internal.h"
 
+#define FORK_FLAGS (CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD)
+
 int fork() {
   __bionic_atfork_run_prepare();
 
   pthread_internal_t* self = __get_thread();
-  int flags = CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD;
+
+  // Remember the parent pid and invalidate the cached value while we fork.
+  pid_t parent_pid = self->invalidate_cached_pid();
+
 #if defined(__x86_64__) // sys_clone's last two arguments are flipped on x86-64.
-  int result = syscall(__NR_clone, flags, NULL, NULL, &(self->tid), NULL);
+  int result = syscall(__NR_clone, FORK_FLAGS, NULL, NULL, &(self->tid), NULL);
 #else
-  int result = syscall(__NR_clone, flags, NULL, NULL, NULL, &(self->tid));
+  int result = syscall(__NR_clone, FORK_FLAGS, NULL, NULL, NULL, &(self->tid));
 #endif
   if (result == 0) {
+    self->set_cached_pid(gettid());
     __bionic_atfork_run_child();
   } else {
+    self->set_cached_pid(parent_pid);
     __bionic_atfork_run_parent();
   }
   return result;

libc/bionic/getpid.cpp

@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <unistd.h>
+
+#include "pthread_internal.h"
+
+extern "C" pid_t __getpid();
+
+pid_t getpid() {
+  pthread_internal_t* self = __get_thread();
+
+  // Do we have a valid cached pid?
+  pid_t cached_pid;
+  if (__predict_true(self->get_cached_pid(&cached_pid))) {
+    return cached_pid;
+  }
+
+  // We're still in the dynamic linker or we're in the middle of forking, so ask the kernel.
+  // We don't know whether it's safe to update the cached value, so don't try.
+  return __getpid();
+}

libc/bionic/libc_init_common.cpp

@@ -86,21 +86,24 @@ static size_t get_main_thread_stack_size() {
 void __libc_init_tls(KernelArgumentBlock& args) {
   __libc_auxv = args.auxv;
 
-  uintptr_t stack_top = (__get_sp() & ~(PAGE_SIZE - 1)) + PAGE_SIZE;
-  size_t stack_size = get_main_thread_stack_size();
-  uintptr_t stack_bottom = stack_top - stack_size;
-
   static void* tls[BIONIC_TLS_SLOTS];
   static pthread_internal_t main_thread;
   main_thread.tls = tls;
 
   // Tell the kernel to clear our tid field when we exit, so we're like any other pthread.
+  // As a side-effect, this tells us our pid (which is the same as the main thread's tid).
   main_thread.tid = __set_tid_address(&main_thread.tid);
+  main_thread.set_cached_pid(main_thread.tid);
 
-  // We already have a stack, and we don't want to free it up on exit (because things like
-  // environment variables with global scope live on it).
+  // Work out the extent of the main thread's stack.
+  uintptr_t stack_top = (__get_sp() & ~(PAGE_SIZE - 1)) + PAGE_SIZE;
+  size_t stack_size = get_main_thread_stack_size();
+  void* stack_bottom = reinterpret_cast<void*>(stack_top - stack_size);
+
+  // We don't want to free the main thread's stack even when the main thread exits
+  // because things like environment variables with global scope live on it.
   pthread_attr_init(&main_thread.attr);
-  pthread_attr_setstack(&main_thread.attr, (void*) stack_bottom, stack_size);
+  pthread_attr_setstack(&main_thread.attr, stack_bottom, stack_size);
   main_thread.attr.flags = PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK | PTHREAD_ATTR_FLAG_MAIN_THREAD;
 
   __init_thread(&main_thread, false);

libc/bionic/pthread_create.cpp

@@ -30,6 +30,7 @@
 
 #include <errno.h>
 #include <sys/mman.h>
+#include <unistd.h>
 
 #include "pthread_internal.h"
 
@@ -220,6 +221,8 @@ int pthread_create(pthread_t* thread_out, pthread_attr_t const* attr,
   thread->start_routine = start_routine;
   thread->start_routine_arg = arg;
 
+  thread->set_cached_pid(getpid());
+
   int flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM |
       CLONE_SETTLS | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID;
   void* tls = thread->tls;

libc/bionic/pthread_internal.h

@@ -36,6 +36,26 @@ struct pthread_internal_t {
 
   pid_t tid;
 
+ private:
+  pid_t cached_pid_;
+
+ public:
+  pid_t invalidate_cached_pid() {
+    pid_t old_value;
+    get_cached_pid(&old_value);
+    set_cached_pid(0);
+    return old_value;
+  }
+
+  void set_cached_pid(pid_t value) {
+    cached_pid_ = value;
+  }
+
+  bool get_cached_pid(pid_t* cached_pid) {
+    *cached_pid = cached_pid_;
+    return (*cached_pid != 0);
+  }
+
   void** tls;
 
   pthread_attr_t attr;

tests/unistd_test.cpp

@@ -22,6 +22,7 @@
 #include <fcntl.h>
 #include <stdint.h>
 #include <unistd.h>
+#include <sys/syscall.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 
@@ -379,3 +380,47 @@ TEST(unistd, fdatasync) {
 TEST(unistd, fsync) {
   TestFsyncFunction(fsync);
 }
+
+TEST(unistd, getpid_caching_and_fork) {
+  pid_t parent_pid = getpid();
+  ASSERT_EQ(syscall(__NR_getpid), parent_pid);
+
+  pid_t fork_result = fork();
+  ASSERT_NE(fork_result, -1);
+  if (fork_result == 0) {
+    // We're the child.
+    ASSERT_EQ(syscall(__NR_getpid), getpid());
+    ASSERT_EQ(parent_pid, getppid());
+    _exit(123);
+  } else {
+    // We're the parent.
+    ASSERT_EQ(parent_pid, getpid());
+
+    int status;
+    ASSERT_EQ(fork_result, waitpid(fork_result, &status, 0));
+    ASSERT_TRUE(WIFEXITED(status));
+    ASSERT_EQ(123, WEXITSTATUS(status));
+  }
+}
+
+static void GetPidCachingHelperHelper() {
+  ASSERT_EQ(syscall(__NR_getpid), getpid());
+}
+
+static void* GetPidCachingHelper(void*) {
+  GetPidCachingHelperHelper(); // Can't assert in a non-void function.
+  return NULL;
+}
+
+TEST(unistd, getpid_caching_and_pthread_create) {
+  pid_t parent_pid = getpid();
+
+  pthread_t t;
+  ASSERT_EQ(0, pthread_create(&t, NULL, GetPidCachingHelper, NULL));
+
+  ASSERT_EQ(parent_pid, getpid());
+
+  void* result;
+  ASSERT_EQ(0, pthread_join(t, &result));
+  ASSERT_EQ(NULL, result);
+}