runtime/cgo: store M for C-created thread in pthread key

[gostls13.git] / src / runtime / asm_amd64.s

diff --git a/src/runtime/asm_amd64.s b/src/runtime/asm_amd64.s
index 0603934cb8bf2caffbe9379a9f6a735fc03558b2..b4c03d7624fd7d44770f76f9603598b2f9e5b9ea 100644 (file)
--- a/src/runtime/asm_amd64.s
+++ b/src/runtime/asm_amd64.s
@@ -918,7 +918,20 @@ GLOBL zeroTLS<>(SB),RODATA,$const_tlsSize
 TEXT ·cgocallback(SB),NOSPLIT,$24-24
        NO_LOCAL_POINTERS
 
-       // If g is nil, Go did not create the current thread.
+       // Skip cgocallbackg, just dropm when fn is nil, and frame is the saved g.
+       // It is used to dropm while thread is exiting.
+       MOVQ    fn+0(FP), AX
+       CMPQ    AX, $0
+       JNE     loadg
+       // Restore the g from frame.
+       get_tls(CX)
+       MOVQ    frame+8(FP), BX
+       MOVQ    BX, g(CX)
+       JMP     dropm
+
+loadg:
+       // If g is nil, Go did not create the current thread,
+       // or if this thread never called into Go on pthread platforms.
        // Call needm to obtain one m for temporary use.
        // In this case, we're running on the thread stack, so there's
        // lots of space, but the linker doesn't know. Hide the call from
@@ -956,9 +969,9 @@ needm:
        // a bad value in there, in case needm tries to use it.
        XORPS   X15, X15
        XORQ    R14, R14
-       MOVQ    $runtime·needm<ABIInternal>(SB), AX
+       MOVQ    $runtime·needAndBindM<ABIInternal>(SB), AX
        CALL    AX
-       MOVQ    $0, savedm-8(SP) // dropm on return
+       MOVQ    $0, savedm-8(SP)
        get_tls(CX)
        MOVQ    g(CX), BX
        MOVQ    g_m(BX), BX
@@ -1047,11 +1060,26 @@ havem:
        MOVQ    0(SP), AX
        MOVQ    AX, (g_sched+gobuf_sp)(SI)
 
-       // If the m on entry was nil, we called needm above to borrow an m
-       // for the duration of the call. Since the call is over, return it with dropm.
+       // If the m on entry was nil, we called needm above to borrow an m,
+       // 1. for the duration of the call on non-pthread platforms,
+       // 2. or the duration of the C thread alive on pthread platforms.
+       // If the m on entry wasn't nil,
+       // 1. the thread might be a Go thread,
+       // 2. or it's wasn't the first call from a C thread on pthread platforms,
+       //    since the we skip dropm to resue the m in the first call.
        MOVQ    savedm-8(SP), BX
        CMPQ    BX, $0
        JNE     done
+
+       // Skip dropm to reuse it in the next call, when a pthread key has been created.
+       MOVQ    _cgo_pthread_key_created(SB), AX
+       // It means cgo is disabled when _cgo_pthread_key_created is a nil pointer, need dropm.
+       CMPQ    AX, $0
+       JEQ     dropm
+       CMPQ    (AX), $0
+       JNE     done
+
+dropm:
        MOVQ    $runtime·dropm(SB), AX
        CALL    AX
 #ifdef GOOS_windows