diff --git a/libc/Android.mk b/libc/Android.mk
index 49c8731..410f242 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -353,6 +353,7 @@
 	arch-arm/bionic/kill.S \
 	arch-arm/bionic/libgcc_compat.c \
 	arch-arm/bionic/tkill.S \
+	arch-arm/bionic/tgkill.S \
 	arch-arm/bionic/memcmp.S \
 	arch-arm/bionic/memcmp16.S \
 	arch-arm/bionic/memcpy.S \
diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index 46e7b1f..fa02edc 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -63,6 +63,7 @@
 # see comments in arch-arm/bionic/kill.S to understand why we don't generate an ARM stub for kill/tkill
 int     kill(pid_t, int)           -1,37
 int     tkill(pid_t tid, int sig)  -1,238
+int     tgkill(pid_t tgid, pid_t tid, int sig)  -1,270
 int     __ptrace:ptrace(int request, int pid, void* addr, void* data)  26
 int     __set_thread_area:set_thread_area(void*  user_desc)  -1,243
 int     __getpriority:getpriority(int, int)  96
diff --git a/libc/arch-arm/bionic/tgkill.S b/libc/arch-arm/bionic/tgkill.S
new file mode 100644
index 0000000..da5c0af
--- /dev/null
+++ b/libc/arch-arm/bionic/tgkill.S
@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2008 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.
+ */
+/* unlike our auto-generated syscall stubs, this code saves lr
+   on the stack, as well as a few other registers. this makes
+   our stack unwinder happy, when we generate debug stack
+   traces after the C library or other parts of the system
+   abort due to a fatal runtime error (e.g. detection
+   of a corrupted malloc heap).
+*/
+
+#include <sys/linux-syscalls.h>
+#include <machine/asm.h>
+
+#ifndef __NR_tgkill
+#define __NR_tgkill  268
+#endif
+
+ENTRY(tgkill)
+    stmfd   sp!, {r4-r7, ip, lr}
+    ldr     r7, =__NR_tgkill
+    swi     #0
+    ldmfd   sp!, {r4-r7, ip, lr}
+    movs    r0, r0
+    bxpl    lr
+    b       __set_syscall_errno
+END(tgkill)
diff --git a/libc/arch-sh/syscalls.mk b/libc/arch-sh/syscalls.mk
index 1d87600..d4e4583 100644
--- a/libc/arch-sh/syscalls.mk
+++ b/libc/arch-sh/syscalls.mk
@@ -26,6 +26,7 @@
 syscall_src += arch-sh/syscalls/__brk.S
 syscall_src += arch-sh/syscalls/kill.S
 syscall_src += arch-sh/syscalls/tkill.S
+syscall_src += arch-sh/syscalls/tgkill.S
 syscall_src += arch-sh/syscalls/__ptrace.S
 syscall_src += arch-sh/syscalls/__set_thread_area.S
 syscall_src += arch-sh/syscalls/__getpriority.S
diff --git a/libc/arch-sh/syscalls/tgkill.S b/libc/arch-sh/syscalls/tgkill.S
new file mode 100644
index 0000000..222f836
--- /dev/null
+++ b/libc/arch-sh/syscalls/tgkill.S
@@ -0,0 +1,32 @@
+/* autogenerated by gensyscalls.py */
+#include <sys/linux-syscalls.h>
+
+    .text
+    .type tgkill, @function
+    .globl tgkill
+    .align 4
+
+tgkill:
+
+    /* invoke trap */
+    mov.l   0f, r3  /* trap num */
+    trapa   #(3 + 0x10)
+
+    /* check return value */
+    cmp/pz  r0
+    bt      __NR_tgkill_end
+
+    /* keep error number */
+    sts.l   pr, @-r15
+    mov.l   1f, r1
+    jsr     @r1
+    mov     r0, r4
+    lds.l   @r15+, pr
+
+__NR_tgkill_end:
+    rts
+    nop
+
+    .align  2
+0:  .long   __NR_tgkill
+1:  .long   __set_syscall_errno
diff --git a/libc/arch-x86/syscalls.mk b/libc/arch-x86/syscalls.mk
index 3b85025..13edeb0 100644
--- a/libc/arch-x86/syscalls.mk
+++ b/libc/arch-x86/syscalls.mk
@@ -26,6 +26,7 @@
 syscall_src += arch-x86/syscalls/__brk.S
 syscall_src += arch-x86/syscalls/kill.S
 syscall_src += arch-x86/syscalls/tkill.S
+syscall_src += arch-x86/syscalls/tgkill.S
 syscall_src += arch-x86/syscalls/__ptrace.S
 syscall_src += arch-x86/syscalls/__set_thread_area.S
 syscall_src += arch-x86/syscalls/__getpriority.S
diff --git a/libc/arch-x86/syscalls/tgkill.S b/libc/arch-x86/syscalls/tgkill.S
new file mode 100644
index 0000000..99af740
--- /dev/null
+++ b/libc/arch-x86/syscalls/tgkill.S
@@ -0,0 +1,29 @@
+/* autogenerated by gensyscalls.py */
+#include <sys/linux-syscalls.h>
+
+    .text
+    .type tgkill, @function
+    .globl tgkill
+    .align 4
+
+tgkill:
+    pushl   %ebx
+    pushl   %ecx
+    pushl   %edx
+    mov     16(%esp), %ebx
+    mov     20(%esp), %ecx
+    mov     24(%esp), %edx
+    movl    $__NR_tgkill, %eax
+    int     $0x80
+    cmpl    $-129, %eax
+    jb      1f
+    negl    %eax
+    pushl   %eax
+    call    __set_errno
+    addl    $4, %esp
+    orl     $-1, %eax
+1:
+    popl    %edx
+    popl    %ecx
+    popl    %ebx
+    ret
diff --git a/libc/bionic/pthread.c b/libc/bionic/pthread.c
index b893a12..10fb7b5 100644
--- a/libc/bionic/pthread.c
+++ b/libc/bionic/pthread.c
@@ -1839,7 +1839,7 @@
 }
 
 // man says this should be in <linux/unistd.h>, but it isn't
-extern int tkill(int tid, int sig);
+extern int tgkill(int tgid, int tid, int sig);
 
 int pthread_kill(pthread_t tid, int sig)
 {
@@ -1847,7 +1847,7 @@
     int  old_errno = errno;
     pthread_internal_t * thread = (pthread_internal_t *)tid;
 
-    ret = tkill(thread->kernel_id, sig);
+    ret = tgkill(getpid(), thread->kernel_id, sig);
     if (ret < 0) {
         ret = errno;
         errno = old_errno;
diff --git a/libc/include/sys/linux-syscalls.h b/libc/include/sys/linux-syscalls.h
index 7b74a4b..930508a 100644
--- a/libc/include/sys/linux-syscalls.h
+++ b/libc/include/sys/linux-syscalls.h
@@ -198,6 +198,7 @@
 #define __NR_waitid                       (__NR_SYSCALL_BASE + 284)
 #define __NR_kill                         (__NR_SYSCALL_BASE + 37)
 #define __NR_tkill                        (__NR_SYSCALL_BASE + 238)
+#define __NR_tgkill                       (__NR_SYSCALL_BASE + 270)
 #define __NR_set_thread_area              (__NR_SYSCALL_BASE + 243)
 #define __NR_openat                       (__NR_SYSCALL_BASE + 295)
 #define __NR_madvise                      (__NR_SYSCALL_BASE + 219)
@@ -242,6 +243,7 @@
 #define __NR_waitid                       (__NR_SYSCALL_BASE + 284)
 #define __NR_kill                         (__NR_SYSCALL_BASE + 37)
 #define __NR_tkill                        (__NR_SYSCALL_BASE + 238)
+#define __NR_tgkill                       (__NR_SYSCALL_BASE + 270)
 #define __NR_set_thread_area              (__NR_SYSCALL_BASE + 243)
 #define __NR_vfork                        (__NR_SYSCALL_BASE + 190)
 #define __NR_openat                       (__NR_SYSCALL_BASE + 295)
diff --git a/libc/include/sys/linux-unistd.h b/libc/include/sys/linux-unistd.h
index ae9077f..f463127 100644
--- a/libc/include/sys/linux-unistd.h
+++ b/libc/include/sys/linux-unistd.h
@@ -32,6 +32,7 @@
 void*            __brk (void*);
 int              kill (pid_t, int);
 int              tkill (pid_t tid, int sig);
+int              tgkill (pid_t tgid, pid_t tid, int sig);
 int              __ptrace (int request, int pid, void* addr, void* data);
 int              __set_thread_area (void*  user_desc);
 int              __getpriority (int, int);