Fwd: PROBLEM: serial port receive buffers not being flushed properly
From: [EMAIL PROTECTED] > [1.] PROBLEM: serial port receive buffers not being flushed properly > [2.] After calling tcflush() or ioctl() with the TCFLSH argument, > an ioctl() with the FIONREAD argument reports 0 bytes available > for reading. However, a subsequent select() and read() of the port > returns data. This problem is seen in 2.6.21.1 and 2.6.20, > but is not seen in version 2.6.17.14. Other versions have > not been tested. There is receive buffering between the serial driver and line discipline. The line discipline processes FIONREAD and TCFLSH with regard to the line discipline receive buffers but not the intermediate buffering. In 2.6.17 the intermediate buffering pushed receive data to the line discipline without regard for tty->receive_room, so if the ldisc buffers were full the data was lost. In 2.6.18 the intermediate buffering was changed to hold receive data until the line discipline could accept it. So in 2.6.17 all the extra data you sent was simply discarded and flushing the ldisc buffers cleared all of the receive data. Starting with 2.6.18, flushing the ldisc buffers just allowed the intermediate buffering to start feeding more data to the ldisc. This results in the receive data you see after a TCFLSH. Starting with 2.6.22 TCFLSH is processed by the intermediate buffering as well as the ldisc to eliminate any remaining receive data in the intermediate buffering. -- Paul Fulghum Microgate Systems, Ltd - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Fwd: PROBLEM: serial port receive buffers not being flushed properly
Please reply to the original poster. - Forwarded message from [EMAIL PROTECTED] - From: [EMAIL PROTECTED] To: [EMAIL PROTECTED] Subject: PROBLEM: serial port receive buffers not being flushed properly Date: Fri, 27 Jul 2007 14:51:00 + See attached .txt and .c files. Use that information to fill in all fields of the bug report form, and post it to the mailing list with a subject of "PROBLEM: " for easy identification by the developers. [1.] PROBLEM: serial port receive buffers not being flushed properly [2.] After calling tcflush() or ioctl() with the TCFLSH argument, an ioctl() with the FIONREAD argument reports 0 bytes available for reading. However, a subsequent select() and read() of the port returns data. This problem is seen in 2.6.21.1 and 2.6.20, but is not seen in version 2.6.17.14. Other versions have not been tested. [3.] keywords: serial buffer flush [4.] Kernel version (from /proc/version): 2.6.21.1 [5.] Most recent kernel version which did not have the bug: 2.6.17.14 (others between 2.6.17.14 and 2.6.20 not checked) [6.] No OOPs message applicable. [7.] See attached source file com_buffer_test.c [8.] Environment [8.1.] Linux Pohaku 2.6.21.1 #1 PREEMPT Thu Jul 12 14:43:22 CDT 2007 i486 GNU/Linux Gnu C 3.3.5 Gnu make 3.80 binutils 2.15 util-linux 2.12p mount 2.12p module-init-tools 3.2-pre1 e2fsprogs 1.37 pcmcia-cs 3.2.5 Linux C Library2.3.2 Dynamic linker (ldd) 2.3.2 Procps 3.2.1 Net-tools 1.60 Console-tools 0.2.3 Sh-utils 5.2.1 udev 056 Modules Loaded ipv6 e100 mii genrtc ext3 jbd ide_disk ide_generic ns87415 piix siimage sc1200 generic cy82c693 cs5530 sis5513 via82cxxx rz1000 slc90e66 cmd64x pdc202xx_old hpt34x opti621 trm290 amd74xx hpt366 serverworks atiixp aec62xx triflex alim15x3 pdc202xx_new cs5520 ide_core unix [8.2.] Processor information (from /proc/cpuinfo): processor : 0 vendor_id : AuthenticAMD cpu family : 4 model : 9 model name : 486 DX/4-WB stepping: 4 fdiv_bug: no hlt_bug : no f00f_bug: no coma_bug: no fpu : yes fpu_exception : yes cpuid level : 1 wp : yes flags : fpu bogomips: 49.40 clflush size: 32 [8.3.] Module information (from /proc/modules): ipv6 234848 10 - Live 0xc4c44000 e100 31632 0 - Live 0xc4bbb000 mii 5152 1 e100, Live 0xc4b83000 genrtc 9420 0 - Live 0xc4b99000 ext3 120392 1 - Live 0xc4bdf000 jbd 55976 1 ext3, Live 0xc4bac000 ide_disk 15808 2 - Live 0xc4b94000 ide_generic 1152 0 [permanent], Live 0xc4b81000 ns87415 3956 0 [permanent], Live 0xc487d000 piix 9764 0 [permanent], Live 0xc4b8a000 siimage 10912 0 [permanent], Live 0xc4b86000 sc1200 5152 0 [permanent], Live 0xc487a000 generic 4744 0 [permanent], Live 0xc4872000 cy82c693 4292 0 [permanent], Live 0xc486f000 cs5530 5056 0 [permanent], Live 0xc4867000 sis5513 14568 0 [permanent], Live 0xc4875000 via82cxxx 8676 0 [permanent], Live 0xc486b000 rz1000 2560 0 [permanent], Live 0xc482b000 slc90e66 5344 0 [permanent], Live 0xc4864000 cmd64x 10012 0 [permanent], Live 0xc4837000 pdc202xx_old 9408 0 [permanent], Live 0xc486 hpt34x 4672 0 [permanent], Live 0xc4834000 opti621 4228 0 [permanent], Live 0xc4831000 trm290 3748 0 [permanent], Live 0xc4829000 amd74xx 13308 0 [permanent], Live 0xc485b000 hpt366 15808 0 [permanent], Live 0xc4856000 serverworks 8264 0 [permanent], Live 0xc482d000 atiixp 6064 0 [permanent], Live 0xc4826000 aec62xx 7200 0 [permanent], Live 0xc4812000 triflex 3584 0 [permanent], Live 0xc481d000 alim15x3 11276 0 [permanent], Live 0xc4822000 pdc202xx_new 7744 0 [permanent], Live 0xc480c000 cs5520 4448 0 [permanent], Live 0xc480f000 ide_core 103204 27 ide_disk,ide_generic,ns87415,piix,siimage,sc1200,generic,cy82c693,cs5530,sis5513,via82cxxx,rz1000,slc90e66,cmd64x,pdc202xx_old,hpt34x,opti621,trm290,amd74xx,hpt366,serverworks,atiixp,aec62xx,triflex,alim15x3,pdc202xx_new,cs5520, Live 0xc483b000 unix 25808 2 - Live 0xc4815000 [8.4.] Loaded driver and hardware information (/proc/ioports, /proc/iomem) -001f : dma1 0020-0021 : pic1 0040-0043 : timer0 0050-0053 : timer1 0060-006f : keyboard 0080-008f : dma page reg 00a0-00a1 : pic2 00c0-00df : dma2 00f0-00ff : fpu 01f0-01f7 : ide0 02e8-02ef : serial 02f8-02ff : serial 03c0-03df : vesafb 03e8-03ef : serial 03f6-03f6 : ide0 03f8-03ff : serial 0cf8-0cff : PCI conf1 f900-f9ff : :00:11.0 fd00-fd3f : :00:10.0 fd00-fd3f : e100 -0009e3ff : System RAM 0009e400-0009 : reserved 000a-000b : Video RAM area 000c-000c : Video ROM 000f-000f : System ROM 0010-03ff : System RAM 0010-0026df65 : Kernel code
Fwd: PROBLEM: serial port receive buffers not being flushed properly
From: [EMAIL PROTECTED] [1.] PROBLEM: serial port receive buffers not being flushed properly [2.] After calling tcflush() or ioctl() with the TCFLSH argument, an ioctl() with the FIONREAD argument reports 0 bytes available for reading. However, a subsequent select() and read() of the port returns data. This problem is seen in 2.6.21.1 and 2.6.20, but is not seen in version 2.6.17.14. Other versions have not been tested. There is receive buffering between the serial driver and line discipline. The line discipline processes FIONREAD and TCFLSH with regard to the line discipline receive buffers but not the intermediate buffering. In 2.6.17 the intermediate buffering pushed receive data to the line discipline without regard for tty-receive_room, so if the ldisc buffers were full the data was lost. In 2.6.18 the intermediate buffering was changed to hold receive data until the line discipline could accept it. So in 2.6.17 all the extra data you sent was simply discarded and flushing the ldisc buffers cleared all of the receive data. Starting with 2.6.18, flushing the ldisc buffers just allowed the intermediate buffering to start feeding more data to the ldisc. This results in the receive data you see after a TCFLSH. Starting with 2.6.22 TCFLSH is processed by the intermediate buffering as well as the ldisc to eliminate any remaining receive data in the intermediate buffering. -- Paul Fulghum Microgate Systems, Ltd - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Fwd: PROBLEM: serial port receive buffers not being flushed properly
Please reply to the original poster. - Forwarded message from [EMAIL PROTECTED] - From: [EMAIL PROTECTED] To: [EMAIL PROTECTED] Subject: PROBLEM: serial port receive buffers not being flushed properly Date: Fri, 27 Jul 2007 14:51:00 + See attached .txt and .c files. Use that information to fill in all fields of the bug report form, and post it to the mailing list with a subject of PROBLEM: one line summary from [1.] for easy identification by the developers. [1.] PROBLEM: serial port receive buffers not being flushed properly [2.] After calling tcflush() or ioctl() with the TCFLSH argument, an ioctl() with the FIONREAD argument reports 0 bytes available for reading. However, a subsequent select() and read() of the port returns data. This problem is seen in 2.6.21.1 and 2.6.20, but is not seen in version 2.6.17.14. Other versions have not been tested. [3.] keywords: serial buffer flush [4.] Kernel version (from /proc/version): 2.6.21.1 [5.] Most recent kernel version which did not have the bug: 2.6.17.14 (others between 2.6.17.14 and 2.6.20 not checked) [6.] No OOPs message applicable. [7.] See attached source file com_buffer_test.c [8.] Environment [8.1.] Linux Pohaku 2.6.21.1 #1 PREEMPT Thu Jul 12 14:43:22 CDT 2007 i486 GNU/Linux Gnu C 3.3.5 Gnu make 3.80 binutils 2.15 util-linux 2.12p mount 2.12p module-init-tools 3.2-pre1 e2fsprogs 1.37 pcmcia-cs 3.2.5 Linux C Library2.3.2 Dynamic linker (ldd) 2.3.2 Procps 3.2.1 Net-tools 1.60 Console-tools 0.2.3 Sh-utils 5.2.1 udev 056 Modules Loaded ipv6 e100 mii genrtc ext3 jbd ide_disk ide_generic ns87415 piix siimage sc1200 generic cy82c693 cs5530 sis5513 via82cxxx rz1000 slc90e66 cmd64x pdc202xx_old hpt34x opti621 trm290 amd74xx hpt366 serverworks atiixp aec62xx triflex alim15x3 pdc202xx_new cs5520 ide_core unix [8.2.] Processor information (from /proc/cpuinfo): processor : 0 vendor_id : AuthenticAMD cpu family : 4 model : 9 model name : 486 DX/4-WB stepping: 4 fdiv_bug: no hlt_bug : no f00f_bug: no coma_bug: no fpu : yes fpu_exception : yes cpuid level : 1 wp : yes flags : fpu bogomips: 49.40 clflush size: 32 [8.3.] Module information (from /proc/modules): ipv6 234848 10 - Live 0xc4c44000 e100 31632 0 - Live 0xc4bbb000 mii 5152 1 e100, Live 0xc4b83000 genrtc 9420 0 - Live 0xc4b99000 ext3 120392 1 - Live 0xc4bdf000 jbd 55976 1 ext3, Live 0xc4bac000 ide_disk 15808 2 - Live 0xc4b94000 ide_generic 1152 0 [permanent], Live 0xc4b81000 ns87415 3956 0 [permanent], Live 0xc487d000 piix 9764 0 [permanent], Live 0xc4b8a000 siimage 10912 0 [permanent], Live 0xc4b86000 sc1200 5152 0 [permanent], Live 0xc487a000 generic 4744 0 [permanent], Live 0xc4872000 cy82c693 4292 0 [permanent], Live 0xc486f000 cs5530 5056 0 [permanent], Live 0xc4867000 sis5513 14568 0 [permanent], Live 0xc4875000 via82cxxx 8676 0 [permanent], Live 0xc486b000 rz1000 2560 0 [permanent], Live 0xc482b000 slc90e66 5344 0 [permanent], Live 0xc4864000 cmd64x 10012 0 [permanent], Live 0xc4837000 pdc202xx_old 9408 0 [permanent], Live 0xc486 hpt34x 4672 0 [permanent], Live 0xc4834000 opti621 4228 0 [permanent], Live 0xc4831000 trm290 3748 0 [permanent], Live 0xc4829000 amd74xx 13308 0 [permanent], Live 0xc485b000 hpt366 15808 0 [permanent], Live 0xc4856000 serverworks 8264 0 [permanent], Live 0xc482d000 atiixp 6064 0 [permanent], Live 0xc4826000 aec62xx 7200 0 [permanent], Live 0xc4812000 triflex 3584 0 [permanent], Live 0xc481d000 alim15x3 11276 0 [permanent], Live 0xc4822000 pdc202xx_new 7744 0 [permanent], Live 0xc480c000 cs5520 4448 0 [permanent], Live 0xc480f000 ide_core 103204 27 ide_disk,ide_generic,ns87415,piix,siimage,sc1200,generic,cy82c693,cs5530,sis5513,via82cxxx,rz1000,slc90e66,cmd64x,pdc202xx_old,hpt34x,opti621,trm290,amd74xx,hpt366,serverworks,atiixp,aec62xx,triflex,alim15x3,pdc202xx_new,cs5520, Live 0xc483b000 unix 25808 2 - Live 0xc4815000 [8.4.] Loaded driver and hardware information (/proc/ioports, /proc/iomem) -001f : dma1 0020-0021 : pic1 0040-0043 : timer0 0050-0053 : timer1 0060-006f : keyboard 0080-008f : dma page reg 00a0-00a1 : pic2 00c0-00df : dma2 00f0-00ff : fpu 01f0-01f7 : ide0 02e8-02ef : serial 02f8-02ff : serial 03c0-03df : vesafb 03e8-03ef : serial 03f6-03f6 : ide0 03f8-03ff : serial 0cf8-0cff : PCI conf1 f900-f9ff : :00:11.0 fd00-fd3f : :00:10.0 fd00-fd3f : e100 -0009e3ff : System RAM 0009e400-0009 : reserved 000a-000b : Video RAM area 000c-000c : Video ROM 000f-000f : System ROM 0010-03ff : System RAM
