Re: [PATCH] uart: fix race between uart_put_char() and uart_shutdown()
On Mon, Jun 04, 2018 at 06:01:27PM -0600, Tycho Andersen wrote: > We have reports of the following crash: > > PID: 7 TASK: 88085c6d61c0 CPU: 1 COMMAND: "kworker/u25:0" > #0 [88085c6db710] machine_kexec at 81046239 > #1 [88085c6db760] crash_kexec at 810fc248 > #2 [88085c6db830] oops_end at 81008ae7 > #3 [88085c6db860] no_context at 81050b8f > #4 [88085c6db8b0] __bad_area_nosemaphore at 81050d75 > #5 [88085c6db900] bad_area_nosemaphore at 81050e83 > #6 [88085c6db910] __do_page_fault at 8105132e > #7 [88085c6db9b0] do_page_fault at 8105152c > #8 [88085c6db9c0] page_fault at 81a3f122 > [exception RIP: uart_put_char+149] > RIP: 814b67b5 RSP: 88085c6dba78 RFLAGS: 00010006 > RAX: 0292 RBX: 827c5120 RCX: 0081 > RDX: RSI: 005f RDI: 827c5120 > RBP: 88085c6dba98 R8: 012c R9: 822ea320 > R10: 88085fe4db04 R11: 0001 R12: 881059f9c000 > R13: 0001 R14: 005f R15: 0fba > ORIG_RAX: CS: 0010 SS: 0018 > #9 [88085c6dbaa0] tty_put_char at 81497544 > #10 [88085c6dbac0] do_output_char at 8149c91c > #11 [88085c6dbae0] __process_echoes at 8149cb8b > #12 [88085c6dbb30] commit_echoes at 8149cdc2 > #13 [88085c6dbb60] n_tty_receive_buf_fast at 8149e49b > #14 [88085c6dbbc0] __receive_buf at 8149ef5a > #15 [88085c6dbc20] n_tty_receive_buf_common at 8149f016 > #16 [88085c6dbca0] n_tty_receive_buf2 at 8149f194 > #17 [88085c6dbcb0] flush_to_ldisc at 814a238a > #18 [88085c6dbd50] process_one_work at 81090be2 > #19 [88085c6dbe20] worker_thread at 81091b4d > #20 [88085c6dbeb0] kthread at 81096384 > #21 [88085c6dbf50] ret_from_fork at 81a3d69f > > after slogging through some dissasembly: > > 814b6720 : > 814b6720: 55 push %rbp > 814b6721: 48 89 e5mov%rsp,%rbp > 814b6724: 48 83 ec 20 sub$0x20,%rsp > 814b6728: 48 89 1c 24 mov%rbx,(%rsp) > 814b672c: 4c 89 64 24 08 mov%r12,0x8(%rsp) > 814b6731: 4c 89 6c 24 10 mov%r13,0x10(%rsp) > 814b6736: 4c 89 74 24 18 mov%r14,0x18(%rsp) > 814b673b: e8 b0 8e 58 00 callq 81a3f5f0 > 814b6740: 4c 8b a7 88 02 00 00mov0x288(%rdi),%r12 > 814b6747: 45 31 edxor%r13d,%r13d > 814b674a: 41 89 f6mov%esi,%r14d > 814b674d: 49 83 bc 24 70 01 00cmpq $0x0,0x170(%r12) > 814b6754: 00 00 > 814b6756: 49 8b 9c 24 80 01 00mov0x180(%r12),%rbx > 814b675d: 00 > 814b675e: 74 2f je 814b678f > > 814b6760: 48 89 dfmov%rbx,%rdi > 814b6763: e8 a8 67 58 00 callq 81a3cf10 > <_raw_spin_lock_irqsave> > 814b6768: 41 8b 8c 24 78 01 00mov0x178(%r12),%ecx > 814b676f: 00 > 814b6770: 89 ca mov%ecx,%edx > 814b6772: f7 d2 not%edx > 814b6774: 41 03 94 24 7c 01 00add0x17c(%r12),%edx > 814b677b: 00 > 814b677c: 81 e2 ff 0f 00 00 and$0xfff,%edx > 814b6782: 75 23 jne814b67a7 > > 814b6784: 48 89 c6mov%rax,%rsi > 814b6787: 48 89 dfmov%rbx,%rdi > 814b678a: e8 e1 64 58 00 callq 81a3cc70 > <_raw_spin_unlock_irqrestore> > 814b678f: 44 89 e8mov%r13d,%eax > 814b6792: 48 8b 1c 24 mov(%rsp),%rbx > 814b6796: 4c 8b 64 24 08 mov0x8(%rsp),%r12 > 814b679b: 4c 8b 6c 24 10 mov0x10(%rsp),%r13 > 814b67a0: 4c 8b 74 24 18 mov0x18(%rsp),%r14 > 814b67a5: c9 leaveq > 814b67a6: c3 retq > 814b67a7: 49 8b 94 24 70 01 00mov0x170(%r12),%rdx > 814b67ae: 00 > 814b67af: 48 63 c9movslq %ecx,%rcx > 814b67b2: 41 b5 01mov$0x1,%r13b > 814b67b5: 44 88 34 0a mov%r14b,(%rdx,%rcx,1) > 814b67b9: 41 8b 94 24 78 01 00mov0x178(%r12),%edx > 814b67c0: 00 > 814b67c1: 83 c2 01add$0x1,%edx >
Re: [PATCH] uart: fix race between uart_put_char() and uart_shutdown()
On Mon, Jun 04, 2018 at 06:01:27PM -0600, Tycho Andersen wrote: > We have reports of the following crash: > > PID: 7 TASK: 88085c6d61c0 CPU: 1 COMMAND: "kworker/u25:0" > #0 [88085c6db710] machine_kexec at 81046239 > #1 [88085c6db760] crash_kexec at 810fc248 > #2 [88085c6db830] oops_end at 81008ae7 > #3 [88085c6db860] no_context at 81050b8f > #4 [88085c6db8b0] __bad_area_nosemaphore at 81050d75 > #5 [88085c6db900] bad_area_nosemaphore at 81050e83 > #6 [88085c6db910] __do_page_fault at 8105132e > #7 [88085c6db9b0] do_page_fault at 8105152c > #8 [88085c6db9c0] page_fault at 81a3f122 > [exception RIP: uart_put_char+149] > RIP: 814b67b5 RSP: 88085c6dba78 RFLAGS: 00010006 > RAX: 0292 RBX: 827c5120 RCX: 0081 > RDX: RSI: 005f RDI: 827c5120 > RBP: 88085c6dba98 R8: 012c R9: 822ea320 > R10: 88085fe4db04 R11: 0001 R12: 881059f9c000 > R13: 0001 R14: 005f R15: 0fba > ORIG_RAX: CS: 0010 SS: 0018 > #9 [88085c6dbaa0] tty_put_char at 81497544 > #10 [88085c6dbac0] do_output_char at 8149c91c > #11 [88085c6dbae0] __process_echoes at 8149cb8b > #12 [88085c6dbb30] commit_echoes at 8149cdc2 > #13 [88085c6dbb60] n_tty_receive_buf_fast at 8149e49b > #14 [88085c6dbbc0] __receive_buf at 8149ef5a > #15 [88085c6dbc20] n_tty_receive_buf_common at 8149f016 > #16 [88085c6dbca0] n_tty_receive_buf2 at 8149f194 > #17 [88085c6dbcb0] flush_to_ldisc at 814a238a > #18 [88085c6dbd50] process_one_work at 81090be2 > #19 [88085c6dbe20] worker_thread at 81091b4d > #20 [88085c6dbeb0] kthread at 81096384 > #21 [88085c6dbf50] ret_from_fork at 81a3d69f > > after slogging through some dissasembly: > > 814b6720 : > 814b6720: 55 push %rbp > 814b6721: 48 89 e5mov%rsp,%rbp > 814b6724: 48 83 ec 20 sub$0x20,%rsp > 814b6728: 48 89 1c 24 mov%rbx,(%rsp) > 814b672c: 4c 89 64 24 08 mov%r12,0x8(%rsp) > 814b6731: 4c 89 6c 24 10 mov%r13,0x10(%rsp) > 814b6736: 4c 89 74 24 18 mov%r14,0x18(%rsp) > 814b673b: e8 b0 8e 58 00 callq 81a3f5f0 > 814b6740: 4c 8b a7 88 02 00 00mov0x288(%rdi),%r12 > 814b6747: 45 31 edxor%r13d,%r13d > 814b674a: 41 89 f6mov%esi,%r14d > 814b674d: 49 83 bc 24 70 01 00cmpq $0x0,0x170(%r12) > 814b6754: 00 00 > 814b6756: 49 8b 9c 24 80 01 00mov0x180(%r12),%rbx > 814b675d: 00 > 814b675e: 74 2f je 814b678f > > 814b6760: 48 89 dfmov%rbx,%rdi > 814b6763: e8 a8 67 58 00 callq 81a3cf10 > <_raw_spin_lock_irqsave> > 814b6768: 41 8b 8c 24 78 01 00mov0x178(%r12),%ecx > 814b676f: 00 > 814b6770: 89 ca mov%ecx,%edx > 814b6772: f7 d2 not%edx > 814b6774: 41 03 94 24 7c 01 00add0x17c(%r12),%edx > 814b677b: 00 > 814b677c: 81 e2 ff 0f 00 00 and$0xfff,%edx > 814b6782: 75 23 jne814b67a7 > > 814b6784: 48 89 c6mov%rax,%rsi > 814b6787: 48 89 dfmov%rbx,%rdi > 814b678a: e8 e1 64 58 00 callq 81a3cc70 > <_raw_spin_unlock_irqrestore> > 814b678f: 44 89 e8mov%r13d,%eax > 814b6792: 48 8b 1c 24 mov(%rsp),%rbx > 814b6796: 4c 8b 64 24 08 mov0x8(%rsp),%r12 > 814b679b: 4c 8b 6c 24 10 mov0x10(%rsp),%r13 > 814b67a0: 4c 8b 74 24 18 mov0x18(%rsp),%r14 > 814b67a5: c9 leaveq > 814b67a6: c3 retq > 814b67a7: 49 8b 94 24 70 01 00mov0x170(%r12),%rdx > 814b67ae: 00 > 814b67af: 48 63 c9movslq %ecx,%rcx > 814b67b2: 41 b5 01mov$0x1,%r13b > 814b67b5: 44 88 34 0a mov%r14b,(%rdx,%rcx,1) > 814b67b9: 41 8b 94 24 78 01 00mov0x178(%r12),%edx > 814b67c0: 00 > 814b67c1: 83 c2 01add$0x1,%edx >
Re: [PATCH] uart: fix race between uart_put_char() and uart_shutdown()
On Mon, Jun 04, 2018 at 10:59:36PM -0500, Serge E. Hallyn wrote: > Quoting Tycho Andersen (ty...@tycho.ws): > > Unfortunately, I don't have any insightful thoughts about how to test this. > > Ideas are appreciated :) > > I wonder whether there is something we can do with qemu -serial pipe: ? Good idea. I couldn't get tty_put_char() to trigger nicely, but I just hard coded one to occur, so at least now I know that this doesn't deadlock when called normally. Another suggestion Serge gave off list was to write a kernel module that implemented a driver. I'll see about doing that to see if I can force the original crash. > > Signed-off-by: Tycho Andersen > > Acked-by: Serge Hallyn Thanks! Tycho
Re: [PATCH] uart: fix race between uart_put_char() and uart_shutdown()
On Mon, Jun 04, 2018 at 10:59:36PM -0500, Serge E. Hallyn wrote: > Quoting Tycho Andersen (ty...@tycho.ws): > > Unfortunately, I don't have any insightful thoughts about how to test this. > > Ideas are appreciated :) > > I wonder whether there is something we can do with qemu -serial pipe: ? Good idea. I couldn't get tty_put_char() to trigger nicely, but I just hard coded one to occur, so at least now I know that this doesn't deadlock when called normally. Another suggestion Serge gave off list was to write a kernel module that implemented a driver. I'll see about doing that to see if I can force the original crash. > > Signed-off-by: Tycho Andersen > > Acked-by: Serge Hallyn Thanks! Tycho
Re: [PATCH] uart: fix race between uart_put_char() and uart_shutdown()
Quoting Tycho Andersen (ty...@tycho.ws): > We have reports of the following crash: > > PID: 7 TASK: 88085c6d61c0 CPU: 1 COMMAND: "kworker/u25:0" > #0 [88085c6db710] machine_kexec at 81046239 > #1 [88085c6db760] crash_kexec at 810fc248 > #2 [88085c6db830] oops_end at 81008ae7 > #3 [88085c6db860] no_context at 81050b8f > #4 [88085c6db8b0] __bad_area_nosemaphore at 81050d75 > #5 [88085c6db900] bad_area_nosemaphore at 81050e83 > #6 [88085c6db910] __do_page_fault at 8105132e > #7 [88085c6db9b0] do_page_fault at 8105152c > #8 [88085c6db9c0] page_fault at 81a3f122 > [exception RIP: uart_put_char+149] > RIP: 814b67b5 RSP: 88085c6dba78 RFLAGS: 00010006 > RAX: 0292 RBX: 827c5120 RCX: 0081 > RDX: RSI: 005f RDI: 827c5120 > RBP: 88085c6dba98 R8: 012c R9: 822ea320 > R10: 88085fe4db04 R11: 0001 R12: 881059f9c000 > R13: 0001 R14: 005f R15: 0fba > ORIG_RAX: CS: 0010 SS: 0018 > #9 [88085c6dbaa0] tty_put_char at 81497544 > #10 [88085c6dbac0] do_output_char at 8149c91c > #11 [88085c6dbae0] __process_echoes at 8149cb8b > #12 [88085c6dbb30] commit_echoes at 8149cdc2 > #13 [88085c6dbb60] n_tty_receive_buf_fast at 8149e49b > #14 [88085c6dbbc0] __receive_buf at 8149ef5a > #15 [88085c6dbc20] n_tty_receive_buf_common at 8149f016 > #16 [88085c6dbca0] n_tty_receive_buf2 at 8149f194 > #17 [88085c6dbcb0] flush_to_ldisc at 814a238a > #18 [88085c6dbd50] process_one_work at 81090be2 > #19 [88085c6dbe20] worker_thread at 81091b4d > #20 [88085c6dbeb0] kthread at 81096384 > #21 [88085c6dbf50] ret_from_fork at 81a3d69f > > after slogging through some dissasembly: > > 814b6720 : > 814b6720: 55 push %rbp > 814b6721: 48 89 e5mov%rsp,%rbp > 814b6724: 48 83 ec 20 sub$0x20,%rsp > 814b6728: 48 89 1c 24 mov%rbx,(%rsp) > 814b672c: 4c 89 64 24 08 mov%r12,0x8(%rsp) > 814b6731: 4c 89 6c 24 10 mov%r13,0x10(%rsp) > 814b6736: 4c 89 74 24 18 mov%r14,0x18(%rsp) > 814b673b: e8 b0 8e 58 00 callq 81a3f5f0 > 814b6740: 4c 8b a7 88 02 00 00mov0x288(%rdi),%r12 > 814b6747: 45 31 edxor%r13d,%r13d > 814b674a: 41 89 f6mov%esi,%r14d > 814b674d: 49 83 bc 24 70 01 00cmpq $0x0,0x170(%r12) > 814b6754: 00 00 > 814b6756: 49 8b 9c 24 80 01 00mov0x180(%r12),%rbx > 814b675d: 00 > 814b675e: 74 2f je 814b678f > > 814b6760: 48 89 dfmov%rbx,%rdi > 814b6763: e8 a8 67 58 00 callq 81a3cf10 > <_raw_spin_lock_irqsave> > 814b6768: 41 8b 8c 24 78 01 00mov0x178(%r12),%ecx > 814b676f: 00 > 814b6770: 89 ca mov%ecx,%edx > 814b6772: f7 d2 not%edx > 814b6774: 41 03 94 24 7c 01 00add0x17c(%r12),%edx > 814b677b: 00 > 814b677c: 81 e2 ff 0f 00 00 and$0xfff,%edx > 814b6782: 75 23 jne814b67a7 > > 814b6784: 48 89 c6mov%rax,%rsi > 814b6787: 48 89 dfmov%rbx,%rdi > 814b678a: e8 e1 64 58 00 callq 81a3cc70 > <_raw_spin_unlock_irqrestore> > 814b678f: 44 89 e8mov%r13d,%eax > 814b6792: 48 8b 1c 24 mov(%rsp),%rbx > 814b6796: 4c 8b 64 24 08 mov0x8(%rsp),%r12 > 814b679b: 4c 8b 6c 24 10 mov0x10(%rsp),%r13 > 814b67a0: 4c 8b 74 24 18 mov0x18(%rsp),%r14 > 814b67a5: c9 leaveq > 814b67a6: c3 retq > 814b67a7: 49 8b 94 24 70 01 00mov0x170(%r12),%rdx > 814b67ae: 00 > 814b67af: 48 63 c9movslq %ecx,%rcx > 814b67b2: 41 b5 01mov$0x1,%r13b > 814b67b5: 44 88 34 0a mov%r14b,(%rdx,%rcx,1) > 814b67b9: 41 8b 94 24 78 01 00mov0x178(%r12),%edx > 814b67c0: 00 > 814b67c1: 83 c2 01add$0x1,%edx > 814b67c4: 81 e2 ff 0f
Re: [PATCH] uart: fix race between uart_put_char() and uart_shutdown()
Quoting Tycho Andersen (ty...@tycho.ws): > We have reports of the following crash: > > PID: 7 TASK: 88085c6d61c0 CPU: 1 COMMAND: "kworker/u25:0" > #0 [88085c6db710] machine_kexec at 81046239 > #1 [88085c6db760] crash_kexec at 810fc248 > #2 [88085c6db830] oops_end at 81008ae7 > #3 [88085c6db860] no_context at 81050b8f > #4 [88085c6db8b0] __bad_area_nosemaphore at 81050d75 > #5 [88085c6db900] bad_area_nosemaphore at 81050e83 > #6 [88085c6db910] __do_page_fault at 8105132e > #7 [88085c6db9b0] do_page_fault at 8105152c > #8 [88085c6db9c0] page_fault at 81a3f122 > [exception RIP: uart_put_char+149] > RIP: 814b67b5 RSP: 88085c6dba78 RFLAGS: 00010006 > RAX: 0292 RBX: 827c5120 RCX: 0081 > RDX: RSI: 005f RDI: 827c5120 > RBP: 88085c6dba98 R8: 012c R9: 822ea320 > R10: 88085fe4db04 R11: 0001 R12: 881059f9c000 > R13: 0001 R14: 005f R15: 0fba > ORIG_RAX: CS: 0010 SS: 0018 > #9 [88085c6dbaa0] tty_put_char at 81497544 > #10 [88085c6dbac0] do_output_char at 8149c91c > #11 [88085c6dbae0] __process_echoes at 8149cb8b > #12 [88085c6dbb30] commit_echoes at 8149cdc2 > #13 [88085c6dbb60] n_tty_receive_buf_fast at 8149e49b > #14 [88085c6dbbc0] __receive_buf at 8149ef5a > #15 [88085c6dbc20] n_tty_receive_buf_common at 8149f016 > #16 [88085c6dbca0] n_tty_receive_buf2 at 8149f194 > #17 [88085c6dbcb0] flush_to_ldisc at 814a238a > #18 [88085c6dbd50] process_one_work at 81090be2 > #19 [88085c6dbe20] worker_thread at 81091b4d > #20 [88085c6dbeb0] kthread at 81096384 > #21 [88085c6dbf50] ret_from_fork at 81a3d69f > > after slogging through some dissasembly: > > 814b6720 : > 814b6720: 55 push %rbp > 814b6721: 48 89 e5mov%rsp,%rbp > 814b6724: 48 83 ec 20 sub$0x20,%rsp > 814b6728: 48 89 1c 24 mov%rbx,(%rsp) > 814b672c: 4c 89 64 24 08 mov%r12,0x8(%rsp) > 814b6731: 4c 89 6c 24 10 mov%r13,0x10(%rsp) > 814b6736: 4c 89 74 24 18 mov%r14,0x18(%rsp) > 814b673b: e8 b0 8e 58 00 callq 81a3f5f0 > 814b6740: 4c 8b a7 88 02 00 00mov0x288(%rdi),%r12 > 814b6747: 45 31 edxor%r13d,%r13d > 814b674a: 41 89 f6mov%esi,%r14d > 814b674d: 49 83 bc 24 70 01 00cmpq $0x0,0x170(%r12) > 814b6754: 00 00 > 814b6756: 49 8b 9c 24 80 01 00mov0x180(%r12),%rbx > 814b675d: 00 > 814b675e: 74 2f je 814b678f > > 814b6760: 48 89 dfmov%rbx,%rdi > 814b6763: e8 a8 67 58 00 callq 81a3cf10 > <_raw_spin_lock_irqsave> > 814b6768: 41 8b 8c 24 78 01 00mov0x178(%r12),%ecx > 814b676f: 00 > 814b6770: 89 ca mov%ecx,%edx > 814b6772: f7 d2 not%edx > 814b6774: 41 03 94 24 7c 01 00add0x17c(%r12),%edx > 814b677b: 00 > 814b677c: 81 e2 ff 0f 00 00 and$0xfff,%edx > 814b6782: 75 23 jne814b67a7 > > 814b6784: 48 89 c6mov%rax,%rsi > 814b6787: 48 89 dfmov%rbx,%rdi > 814b678a: e8 e1 64 58 00 callq 81a3cc70 > <_raw_spin_unlock_irqrestore> > 814b678f: 44 89 e8mov%r13d,%eax > 814b6792: 48 8b 1c 24 mov(%rsp),%rbx > 814b6796: 4c 8b 64 24 08 mov0x8(%rsp),%r12 > 814b679b: 4c 8b 6c 24 10 mov0x10(%rsp),%r13 > 814b67a0: 4c 8b 74 24 18 mov0x18(%rsp),%r14 > 814b67a5: c9 leaveq > 814b67a6: c3 retq > 814b67a7: 49 8b 94 24 70 01 00mov0x170(%r12),%rdx > 814b67ae: 00 > 814b67af: 48 63 c9movslq %ecx,%rcx > 814b67b2: 41 b5 01mov$0x1,%r13b > 814b67b5: 44 88 34 0a mov%r14b,(%rdx,%rcx,1) > 814b67b9: 41 8b 94 24 78 01 00mov0x178(%r12),%edx > 814b67c0: 00 > 814b67c1: 83 c2 01add$0x1,%edx > 814b67c4: 81 e2 ff 0f
[PATCH] uart: fix race between uart_put_char() and uart_shutdown()
We have reports of the following crash: PID: 7 TASK: 88085c6d61c0 CPU: 1 COMMAND: "kworker/u25:0" #0 [88085c6db710] machine_kexec at 81046239 #1 [88085c6db760] crash_kexec at 810fc248 #2 [88085c6db830] oops_end at 81008ae7 #3 [88085c6db860] no_context at 81050b8f #4 [88085c6db8b0] __bad_area_nosemaphore at 81050d75 #5 [88085c6db900] bad_area_nosemaphore at 81050e83 #6 [88085c6db910] __do_page_fault at 8105132e #7 [88085c6db9b0] do_page_fault at 8105152c #8 [88085c6db9c0] page_fault at 81a3f122 [exception RIP: uart_put_char+149] RIP: 814b67b5 RSP: 88085c6dba78 RFLAGS: 00010006 RAX: 0292 RBX: 827c5120 RCX: 0081 RDX: RSI: 005f RDI: 827c5120 RBP: 88085c6dba98 R8: 012c R9: 822ea320 R10: 88085fe4db04 R11: 0001 R12: 881059f9c000 R13: 0001 R14: 005f R15: 0fba ORIG_RAX: CS: 0010 SS: 0018 #9 [88085c6dbaa0] tty_put_char at 81497544 #10 [88085c6dbac0] do_output_char at 8149c91c #11 [88085c6dbae0] __process_echoes at 8149cb8b #12 [88085c6dbb30] commit_echoes at 8149cdc2 #13 [88085c6dbb60] n_tty_receive_buf_fast at 8149e49b #14 [88085c6dbbc0] __receive_buf at 8149ef5a #15 [88085c6dbc20] n_tty_receive_buf_common at 8149f016 #16 [88085c6dbca0] n_tty_receive_buf2 at 8149f194 #17 [88085c6dbcb0] flush_to_ldisc at 814a238a #18 [88085c6dbd50] process_one_work at 81090be2 #19 [88085c6dbe20] worker_thread at 81091b4d #20 [88085c6dbeb0] kthread at 81096384 #21 [88085c6dbf50] ret_from_fork at 81a3d69f after slogging through some dissasembly: 814b6720 : 814b6720: 55 push %rbp 814b6721: 48 89 e5mov%rsp,%rbp 814b6724: 48 83 ec 20 sub$0x20,%rsp 814b6728: 48 89 1c 24 mov%rbx,(%rsp) 814b672c: 4c 89 64 24 08 mov%r12,0x8(%rsp) 814b6731: 4c 89 6c 24 10 mov%r13,0x10(%rsp) 814b6736: 4c 89 74 24 18 mov%r14,0x18(%rsp) 814b673b: e8 b0 8e 58 00 callq 81a3f5f0 814b6740: 4c 8b a7 88 02 00 00mov0x288(%rdi),%r12 814b6747: 45 31 edxor%r13d,%r13d 814b674a: 41 89 f6mov%esi,%r14d 814b674d: 49 83 bc 24 70 01 00cmpq $0x0,0x170(%r12) 814b6754: 00 00 814b6756: 49 8b 9c 24 80 01 00mov0x180(%r12),%rbx 814b675d: 00 814b675e: 74 2f je 814b678f 814b6760: 48 89 dfmov%rbx,%rdi 814b6763: e8 a8 67 58 00 callq 81a3cf10 <_raw_spin_lock_irqsave> 814b6768: 41 8b 8c 24 78 01 00mov0x178(%r12),%ecx 814b676f: 00 814b6770: 89 ca mov%ecx,%edx 814b6772: f7 d2 not%edx 814b6774: 41 03 94 24 7c 01 00add0x17c(%r12),%edx 814b677b: 00 814b677c: 81 e2 ff 0f 00 00 and$0xfff,%edx 814b6782: 75 23 jne814b67a7 814b6784: 48 89 c6mov%rax,%rsi 814b6787: 48 89 dfmov%rbx,%rdi 814b678a: e8 e1 64 58 00 callq 81a3cc70 <_raw_spin_unlock_irqrestore> 814b678f: 44 89 e8mov%r13d,%eax 814b6792: 48 8b 1c 24 mov(%rsp),%rbx 814b6796: 4c 8b 64 24 08 mov0x8(%rsp),%r12 814b679b: 4c 8b 6c 24 10 mov0x10(%rsp),%r13 814b67a0: 4c 8b 74 24 18 mov0x18(%rsp),%r14 814b67a5: c9 leaveq 814b67a6: c3 retq 814b67a7: 49 8b 94 24 70 01 00mov0x170(%r12),%rdx 814b67ae: 00 814b67af: 48 63 c9movslq %ecx,%rcx 814b67b2: 41 b5 01mov$0x1,%r13b 814b67b5: 44 88 34 0a mov%r14b,(%rdx,%rcx,1) 814b67b9: 41 8b 94 24 78 01 00mov0x178(%r12),%edx 814b67c0: 00 814b67c1: 83 c2 01add$0x1,%edx 814b67c4: 81 e2 ff 0f 00 00 and$0xfff,%edx 814b67ca: 41 89 94 24 78 01 00mov%edx,0x178(%r12) 814b67d1:
[PATCH] uart: fix race between uart_put_char() and uart_shutdown()
We have reports of the following crash: PID: 7 TASK: 88085c6d61c0 CPU: 1 COMMAND: "kworker/u25:0" #0 [88085c6db710] machine_kexec at 81046239 #1 [88085c6db760] crash_kexec at 810fc248 #2 [88085c6db830] oops_end at 81008ae7 #3 [88085c6db860] no_context at 81050b8f #4 [88085c6db8b0] __bad_area_nosemaphore at 81050d75 #5 [88085c6db900] bad_area_nosemaphore at 81050e83 #6 [88085c6db910] __do_page_fault at 8105132e #7 [88085c6db9b0] do_page_fault at 8105152c #8 [88085c6db9c0] page_fault at 81a3f122 [exception RIP: uart_put_char+149] RIP: 814b67b5 RSP: 88085c6dba78 RFLAGS: 00010006 RAX: 0292 RBX: 827c5120 RCX: 0081 RDX: RSI: 005f RDI: 827c5120 RBP: 88085c6dba98 R8: 012c R9: 822ea320 R10: 88085fe4db04 R11: 0001 R12: 881059f9c000 R13: 0001 R14: 005f R15: 0fba ORIG_RAX: CS: 0010 SS: 0018 #9 [88085c6dbaa0] tty_put_char at 81497544 #10 [88085c6dbac0] do_output_char at 8149c91c #11 [88085c6dbae0] __process_echoes at 8149cb8b #12 [88085c6dbb30] commit_echoes at 8149cdc2 #13 [88085c6dbb60] n_tty_receive_buf_fast at 8149e49b #14 [88085c6dbbc0] __receive_buf at 8149ef5a #15 [88085c6dbc20] n_tty_receive_buf_common at 8149f016 #16 [88085c6dbca0] n_tty_receive_buf2 at 8149f194 #17 [88085c6dbcb0] flush_to_ldisc at 814a238a #18 [88085c6dbd50] process_one_work at 81090be2 #19 [88085c6dbe20] worker_thread at 81091b4d #20 [88085c6dbeb0] kthread at 81096384 #21 [88085c6dbf50] ret_from_fork at 81a3d69f after slogging through some dissasembly: 814b6720 : 814b6720: 55 push %rbp 814b6721: 48 89 e5mov%rsp,%rbp 814b6724: 48 83 ec 20 sub$0x20,%rsp 814b6728: 48 89 1c 24 mov%rbx,(%rsp) 814b672c: 4c 89 64 24 08 mov%r12,0x8(%rsp) 814b6731: 4c 89 6c 24 10 mov%r13,0x10(%rsp) 814b6736: 4c 89 74 24 18 mov%r14,0x18(%rsp) 814b673b: e8 b0 8e 58 00 callq 81a3f5f0 814b6740: 4c 8b a7 88 02 00 00mov0x288(%rdi),%r12 814b6747: 45 31 edxor%r13d,%r13d 814b674a: 41 89 f6mov%esi,%r14d 814b674d: 49 83 bc 24 70 01 00cmpq $0x0,0x170(%r12) 814b6754: 00 00 814b6756: 49 8b 9c 24 80 01 00mov0x180(%r12),%rbx 814b675d: 00 814b675e: 74 2f je 814b678f 814b6760: 48 89 dfmov%rbx,%rdi 814b6763: e8 a8 67 58 00 callq 81a3cf10 <_raw_spin_lock_irqsave> 814b6768: 41 8b 8c 24 78 01 00mov0x178(%r12),%ecx 814b676f: 00 814b6770: 89 ca mov%ecx,%edx 814b6772: f7 d2 not%edx 814b6774: 41 03 94 24 7c 01 00add0x17c(%r12),%edx 814b677b: 00 814b677c: 81 e2 ff 0f 00 00 and$0xfff,%edx 814b6782: 75 23 jne814b67a7 814b6784: 48 89 c6mov%rax,%rsi 814b6787: 48 89 dfmov%rbx,%rdi 814b678a: e8 e1 64 58 00 callq 81a3cc70 <_raw_spin_unlock_irqrestore> 814b678f: 44 89 e8mov%r13d,%eax 814b6792: 48 8b 1c 24 mov(%rsp),%rbx 814b6796: 4c 8b 64 24 08 mov0x8(%rsp),%r12 814b679b: 4c 8b 6c 24 10 mov0x10(%rsp),%r13 814b67a0: 4c 8b 74 24 18 mov0x18(%rsp),%r14 814b67a5: c9 leaveq 814b67a6: c3 retq 814b67a7: 49 8b 94 24 70 01 00mov0x170(%r12),%rdx 814b67ae: 00 814b67af: 48 63 c9movslq %ecx,%rcx 814b67b2: 41 b5 01mov$0x1,%r13b 814b67b5: 44 88 34 0a mov%r14b,(%rdx,%rcx,1) 814b67b9: 41 8b 94 24 78 01 00mov0x178(%r12),%edx 814b67c0: 00 814b67c1: 83 c2 01add$0x1,%edx 814b67c4: 81 e2 ff 0f 00 00 and$0xfff,%edx 814b67ca: 41 89 94 24 78 01 00mov%edx,0x178(%r12) 814b67d1:
