On 3/2/16, Peter Zijlstra <[email protected]> wrote: > On Wed, Mar 02, 2016 at 04:53:36PM +0100, Sedat Dilek wrote: >> ffffffff8110f570 <del_timer_sync>: >> ffffffff8110f570: 55 push %rbp >> ffffffff8110f571: 48 89 e5 mov %rsp,%rbp >> ffffffff8110f574: 41 57 push %r15 >> ffffffff8110f576: 41 56 push %r14 >> ffffffff8110f578: 53 push %rbx >> ffffffff8110f579: 48 83 ec 28 sub $0x28,%rsp > > stack offset is 0x28 bytes [*] > >> ffffffff8110f57d: 48 89 fb mov %rdi,%rbx >> ffffffff8110f580: e8 6b 6e 80 00 callq ffffffff819163f0 <mcount> >> ffffffff8110f585: e8 66 6e 80 00 callq ffffffff819163f0 <mcount> >> ffffffff8110f58a: e8 61 6e 80 00 callq ffffffff819163f0 <mcount> >> ffffffff8110f58f: e8 5c 6e 80 00 callq ffffffff819163f0 <mcount> > > Your compiler is on drugs! > >> ffffffff8110f594: 9c pushfq >> ffffffff8110f595: 8f 45 e0 popq -0x20(%rbp) > > Saves flags in -0x20(%rbp) > >> ffffffff8110f598: 4c 8b 7d e0 mov -0x20(%rbp),%r15 > > And in %r15 > > /me wonders what's wrong with: popf %r15 > >> ffffffff8110f59c: e8 4f 6e 80 00 callq ffffffff819163f0 <mcount> >> ffffffff8110f5a1: e8 4a 6e 80 00 callq ffffffff819163f0 <mcount> >> ffffffff8110f5a6: fa cli >> ffffffff8110f5a7: e8 84 cb fc ff callq ffffffff810dc130 >> <trace_hardirqs_off> >> ffffffff8110f5ac: 4c 8d 73 50 lea 0x50(%rbx),%r14 >> ffffffff8110f5b0: 48 c7 04 24 b0 f5 10 movq >> $0xffffffff8110f5b0,(%rsp) >> ffffffff8110f5b7: 81 >> ffffffff8110f5b8: 31 f6 xor %esi,%esi >> ffffffff8110f5ba: 31 d2 xor %edx,%edx >> ffffffff8110f5bc: 31 c9 xor %ecx,%ecx >> ffffffff8110f5be: 41 b8 01 00 00 00 mov $0x1,%r8d >> ffffffff8110f5c4: 45 31 c9 xor %r9d,%r9d >> ffffffff8110f5c7: 4c 89 f7 mov %r14,%rdi >> ffffffff8110f5ca: e8 c1 e5 fc ff callq ffffffff810ddb90 >> <lock_acquire> >> ffffffff8110f5cf: be 01 00 00 00 mov $0x1,%esi >> ffffffff8110f5d4: 48 c7 c2 cf f5 10 81 mov $0xffffffff8110f5cf,%rdx >> ffffffff8110f5db: 4c 89 f7 mov %r14,%rdi >> ffffffff8110f5de: e8 8d 08 fd ff callq ffffffff810dfe70 >> <lock_release> >> ffffffff8110f5e3: e8 08 6e 80 00 callq ffffffff819163f0 <mcount> > >> ffffffff8110f5e8: 4c 89 f8 mov %r15,%rax >> ffffffff8110f5eb: 49 89 c6 mov %rax,%r14 > > Moves r15 into r14 through rax > > >> ffffffff8110f5ee: f6 c4 02 test $0x2,%ah >> ffffffff8110f5f1: 75 19 jne ffffffff8110f60c >> <del_timer_sync+0x9c> >> ffffffff8110f5f3: e8 f8 6d 80 00 callq ffffffff819163f0 <mcount> >> ffffffff8110f5f8: e8 f3 6d 80 00 callq ffffffff819163f0 <mcount> > > >> ffffffff8110f5fd: 4c 89 75 d0 mov %r14,-0x30(%rbp) >> ffffffff8110f601: ff 75 d0 pushq -0x30(%rbp) >> ffffffff8110f604: 9d popfq > > put r14 into -0x30(rbp) and pushes/pops that, see [*] this is 8 bytes > over stack ?! > >> ffffffff8110f605: e8 26 cb fc ff callq ffffffff810dc130 >> <trace_hardirqs_off> >> ffffffff8110f60a: eb 17 jmp ffffffff8110f623 >> <del_timer_sync+0xb3> >> ffffffff8110f60c: e8 2f cb fc ff callq ffffffff810dc140 >> <trace_hardirqs_on> >> ffffffff8110f611: e8 da 6d 80 00 callq ffffffff819163f0 <mcount> >> ffffffff8110f616: e8 d5 6d 80 00 callq ffffffff819163f0 <mcount> >> ffffffff8110f61b: 4c 89 75 d8 mov %r14,-0x28(%rbp) >> ffffffff8110f61f: ff 75 d8 pushq -0x28(%rbp) >> ffffffff8110f622: 9d popfq > > puts r14 into -0x28(rbp) and pushes/pops that > >> ffffffff8110f623: e8 c8 6d 80 00 callq ffffffff819163f0 <mcount> >> ffffffff8110f628: 65 8b 04 25 d4 ae 00 mov %gs:0xaed4,%eax >> ffffffff8110f62f: 00 >> ffffffff8110f630: a9 00 00 0f 00 test $0xf0000,%eax >> ffffffff8110f635: 74 25 je ffffffff8110f65c >> <del_timer_sync+0xec> >> ffffffff8110f637: f6 43 2a 20 testb $0x20,0x2a(%rbx) >> ffffffff8110f63b: 75 1f jne ffffffff8110f65c >> <del_timer_sync+0xec> >> ffffffff8110f63d: 48 c7 c7 04 54 c5 81 mov $0xffffffff81c55404,%rdi >> ffffffff8110f644: be 61 04 00 00 mov $0x461,%esi >> ffffffff8110f649: e8 12 c4 f6 ff callq ffffffff8107ba60 >> <warn_slowpath_null> >> ffffffff8110f64e: eb 0c jmp ffffffff8110f65c >> <del_timer_sync+0xec> >> ffffffff8110f650: e8 9b 6d 80 00 callq ffffffff819163f0 <mcount> >> ffffffff8110f655: e8 96 6d 80 00 callq ffffffff819163f0 <mcount> >> ffffffff8110f65a: f3 90 pause >> ffffffff8110f65c: 48 89 df mov %rbx,%rdi >> ffffffff8110f65f: e8 4c fe ff ff callq ffffffff8110f4b0 >> <try_to_del_timer_sync> >> ffffffff8110f664: 85 c0 test %eax,%eax >> ffffffff8110f666: 78 e8 js ffffffff8110f650 >> <del_timer_sync+0xe0> >> ffffffff8110f668: 48 83 c4 28 add $0x28,%rsp >> ffffffff8110f66c: 5b pop %rbx >> ffffffff8110f66d: 41 5e pop %r14 >> ffffffff8110f66f: 41 5f pop %r15 >> ffffffff8110f671: 5d pop %rbp >> ffffffff8110f672: c3 retq >> ffffffff8110f673: 66 66 66 66 2e 0f 1f data32 data32 data32 nopw >> %cs:0x0(%rax,%rax,1) >> ffffffff8110f67a: 84 00 00 00 00 00 > > > That LLVM generate disgusting code, as a contrast, this is what my GCC > makes of this: > > ffffffff81155f50 <del_timer_sync>: > ffffffff81155f50: e8 bb 02 9c 00 callq ffffffff81b16210 > <__fentry__> > ffffffff81155f55: 55 push %rbp > ffffffff81155f56: 48 89 e5 mov %rsp,%rbp > ffffffff81155f59: 41 55 push %r13 > ffffffff81155f5b: 41 54 push %r12 > ffffffff81155f5d: 53 push %rbx > ffffffff81155f5e: 48 89 fb mov %rdi,%rbx > ffffffff81155f61: 48 83 ec 08 sub $0x8,%rsp > ffffffff81155f65: 9c pushfq > ffffffff81155f66: 41 5c pop %r12 > ffffffff81155f68: fa cli > ffffffff81155f69: e8 72 5c fd ff callq ffffffff8112bbe0 > <trace_hardirqs_off> > ffffffff81155f6e: 4c 8d 6b 50 lea 0x50(%rbx),%r13 > ffffffff81155f72: 45 31 c9 xor %r9d,%r9d > ffffffff81155f75: 31 c9 xor %ecx,%ecx > ffffffff81155f77: 31 d2 xor %edx,%edx > ffffffff81155f79: 31 f6 xor %esi,%esi > ffffffff81155f7b: 4c 89 ef mov %r13,%rdi > ffffffff81155f7e: 48 c7 04 24 55 5f 15 movq > $0xffffffff81155f55,(%rsp) > ffffffff81155f85: 81 > ffffffff81155f86: 41 b8 01 00 00 00 mov $0x1,%r8d > ffffffff81155f8c: e8 3f b3 fd ff callq ffffffff811312d0 > <lock_acquire> > ffffffff81155f91: 48 c7 c2 55 5f 15 81 mov > $0xffffffff81155f55,%rdx > ffffffff81155f98: be 01 00 00 00 mov $0x1,%esi > ffffffff81155f9d: 4c 89 ef mov %r13,%rdi > ffffffff81155fa0: e8 0b b5 fd ff callq ffffffff811314b0 > <lock_release> > ffffffff81155fa5: 41 f7 c4 00 02 00 00 test $0x200,%r12d > ffffffff81155fac: 75 52 jne ffffffff81156000 > <del_timer_sync+0xb0> > ffffffff81155fae: 41 54 push %r12 > ffffffff81155fb0: 9d popfq > ffffffff81155fb1: e8 2a 5c fd ff callq ffffffff8112bbe0 > <trace_hardirqs_off> > ffffffff81155fb6: 65 8b 05 5b 66 eb 7e mov > %gs:0x7eeb665b(%rip),%eax # c618 <__preempt_count> > ffffffff81155fbd: a9 00 00 0f 00 test $0xf0000,%eax > ffffffff81155fc2: 74 25 je ffffffff81155fe9 > <del_timer_sync+0x99> > ffffffff81155fc4: f6 43 2a 20 testb $0x20,0x2a(%rbx) > ffffffff81155fc8: 75 1f jne ffffffff81155fe9 > <del_timer_sync+0x99> > ffffffff81155fca: be 61 04 00 00 mov $0x461,%esi > ffffffff81155fcf: 48 c7 c7 09 87 f3 81 mov > $0xffffffff81f38709,%rdi > ffffffff81155fd6: e8 15 03 f8 ff callq ffffffff810d62f0 > <warn_slowpath_null> > ffffffff81155fdb: 48 89 df mov %rbx,%rdi > ffffffff81155fde: e8 fd fe ff ff callq ffffffff81155ee0 > <try_to_del_timer_sync> > ffffffff81155fe3: 85 c0 test %eax,%eax > ffffffff81155fe5: 79 0e jns ffffffff81155ff5 > <del_timer_sync+0xa5> > ffffffff81155fe7: f3 90 pause > ffffffff81155fe9: 48 89 df mov %rbx,%rdi > ffffffff81155fec: e8 ef fe ff ff callq ffffffff81155ee0 > <try_to_del_timer_sync> > ffffffff81155ff1: 85 c0 test %eax,%eax > ffffffff81155ff3: 78 f2 js ffffffff81155fe7 > <del_timer_sync+0x97> > ffffffff81155ff5: 48 83 c4 08 add $0x8,%rsp > ffffffff81155ff9: 5b pop %rbx > ffffffff81155ffa: 41 5c pop %r12 > ffffffff81155ffc: 41 5d pop %r13 > ffffffff81155ffe: 5d pop %rbp > ffffffff81155fff: c3 retq > ffffffff81156000: e8 4b 8b fd ff callq ffffffff8112eb50 > <trace_hardirqs_on> > ffffffff81156005: 41 54 push %r12 > ffffffff81156007: 9d popfq > ffffffff81156008: eb ac jmp ffffffff81155fb6 > <del_timer_sync+0x66> > ffffffff8115600a: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1) >
OK, I cannot say much to your analysis. The full make-lines look differently. GCC for example has '-mfentry -DCC_USING_FENTRY'. [ CLANG ] mycompiler -Wp,-MD,kernel/.workqueue.o.d -nostdinc -isystem /opt/llvm-toolchain-3.8.0rc3/bin/../lib/clang/3.8.0/include -nostdinc -isystem /opt/llvm-toolchain-3.8.0rc3/bin/../lib/clang/3.8.0/include -I./arch/x86/include -Iarch/x86/include/generated/uapi -Iarch/x86/include/generated -Iinclude -I./arch/x86/include/uapi -Iarch/x86/include/generated/uapi -I./include/uapi -Iinclude/generated/uapi -include ./include/linux/kconfig.h -D__KERNEL__ -Qunused-arguments -Wno-unknown-warning-option -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -Wno-format-security -std=gnu89 -no-integrated-as -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -m64 -mtune=generic -mno-red-zone -mcmodel=kernel -funit-at-a-time -DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -DCONFIG_AS_CFI_SECTIONS=1 -DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1 -DCONFIG_AS_CRC32=1 -DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1 -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -O2 -Wframe-larger-than=1024 -fno-stack-protector -Wno-unused-variable -Wno-format-invalid-specifier -Wno-gnu -Wno-asm-operand-widths -Wno-initializer-overrides -fno-builtin -Wno-tautological-compare -mno-global-merge -fno-omit-frame-pointer -fno-optimize-sibling-calls -pg -Wdeclaration-after-statement -Wno-pointer-sign -fno-strict-overflow -Werror=implicit-int -Werror=strict-prototypes -Werror=date-time -Wno-initializer-overrides -Wno-unused-value -Wno-format -Wno-unknown-warning-option -Wno-sign-compare -Wno-format-zero-length -Wno-uninitialized -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(workqueue)" -D"KBUILD_MODNAME=KBUILD_STR(workqueue)" -c -o kernel/.tmp_workqueue.o kernel/workqueue.c mycompiler -Wp,-MD,kernel/time/.timer.o.d -nostdinc -isystem /opt/llvm-toolchain-3.8.0rc3/bin/../lib/clang/3.8.0/include -nostdinc -isystem /opt/llvm-toolchain-3.8.0rc3/bin/../lib/clang/3.8.0/include -I./arch/x86/include -Iarch/x86/include/generated/uapi -Iarch/x86/include/generated -Iinclude -I./arch/x86/include/uapi -Iarch/x86/include/generated/uapi -I./include/uapi -Iinclude/generated/uapi -include ./include/linux/kconfig.h -D__KERNEL__ -Qunused-arguments -Wno-unknown-warning-option -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -Wno-format-security -std=gnu89 -no-integrated-as -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -m64 -mtune=generic -mno-red-zone -mcmodel=kernel -funit-at-a-time -DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -DCONFIG_AS_CFI_SECTIONS=1 -DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1 -DCONFIG_AS_CRC32=1 -DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1 -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -O2 -Wframe-larger-than=1024 -fno-stack-protector -Wno-unused-variable -Wno-format-invalid-specifier -Wno-gnu -Wno-asm-operand-widths -Wno-initializer-overrides -fno-builtin -Wno-tautological-compare -mno-global-merge -fno-omit-frame-pointer -fno-optimize-sibling-calls -pg -Wdeclaration-after-statement -Wno-pointer-sign -fno-strict-overflow -Werror=implicit-int -Werror=strict-prototypes -Werror=date-time -Wno-initializer-overrides -Wno-unused-value -Wno-format -Wno-unknown-warning-option -Wno-sign-compare -Wno-format-zero-length -Wno-uninitialized -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(timer)" -D"KBUILD_MODNAME=KBUILD_STR(timer)" -c -o kernel/time/.tmp_timer.o kernel/time/timer.c [ GCC ] mycompiler -Wp,-MD,kernel/.workqueue.o.d -nostdinc -isystem /usr/lib/gcc/x86_64-linux-gnu/4.9/include -nostdinc -isystem /usr/lib/gcc/x86_64-linux-gnu/4.9/include -I./arch/x86/include -Iarch/x86/include/generated/uapi -Iarch/x86/include/generated -Iinclude -I./arch/x86/include/uapi -Iarch/x86/include/generated/uapi -I./include/uapi -Iinclude/generated/uapi -include ./include/linux/kconfig.h -D__KERNEL__ -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -Wno-format-security -std=gnu89 -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -m64 -falign-jumps=1 -falign-loops=1 -mno-80387 -mno-fp-ret-in-387 -mpreferred-stack-boundary=3 -mtune=generic -mno-red-zone -mcmodel=kernel -funit-at-a-time -maccumulate-outgoing-args -DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -DCONFIG_AS_CFI_SECTIONS=1 -DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1 -DCONFIG_AS_CRC32=1 -DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1 -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -fno-delete-null-pointer-checks -O2 --param=allow-store-data-races=0 -Wframe-larger-than=1024 -fno-stack-protector -Wno-unused-but-set-variable -fno-omit-frame-pointer -fno-optimize-sibling-calls -fno-var-tracking-assignments -pg -mfentry -DCC_USING_FENTRY -Wdeclaration-after-statement -Wno-pointer-sign -fno-strict-overflow -fconserve-stack -Werror=implicit-int -Werror=strict-prototypes -Werror=date-time -DCC_HAVE_ASM_GOTO -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(workqueue)" -D"KBUILD_MODNAME=KBUILD_STR(workqueue)" -c -o kernel/.tmp_workqueue.o kernel/workqueue.c mycompiler -Wp,-MD,kernel/time/.timer.o.d -nostdinc -isystem /usr/lib/gcc/x86_64-linux-gnu/4.9/include -nostdinc -isystem /usr/lib/gcc/x86_64-linux-gnu/4.9/include -I./arch/x86/include -Iarch/x86/include/generated/uapi -Iarch/x86/include/generated -Iinclude -I./arch/x86/include/uapi -Iarch/x86/include/generated/uapi -I./include/uapi -Iinclude/generated/uapi -include ./include/linux/kconfig.h -D__KERNEL__ -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -Wno-format-security -std=gnu89 -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -m64 -falign-jumps=1 -falign-loops=1 -mno-80387 -mno-fp-ret-in-387 -mpreferred-stack-boundary=3 -mtune=generic -mno-red-zone -mcmodel=kernel -funit-at-a-time -maccumulate-outgoing-args -DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -DCONFIG_AS_CFI_SECTIONS=1 -DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1 -DCONFIG_AS_CRC32=1 -DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1 -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -fno-delete-null-pointer-checks -O2 --param=allow-store-data-races=0 -Wframe-larger-than=1024 -fno-stack-protector -Wno-unused-but-set-variable -fno-omit-frame-pointer -fno-optimize-sibling-calls -fno-var-tracking-assignments -pg -mfentry -DCC_USING_FENTRY -Wdeclaration-after-statement -Wno-pointer-sign -fno-strict-overflow -fconserve-stack -Werror=implicit-int -Werror=strict-prototypes -Werror=date-time -DCC_HAVE_ASM_GOTO -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(timer)" -D"KBUILD_MODNAME=KBUILD_STR(timer)" -c -o kernel/time/.tmp_timer.o kernel/time/timer.c I can try to use the make-line of GCC and re-compile. - Sedat -
