- 23 Jul, 2013 35 commits
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Peter Hurley authored
Signed-off-by:
Peter Hurley <peter@hurleysoftware.com> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Peter Hurley authored
tty_buffer_find() implements a simple free list lookaside cache. Merge this functionality into tty_buffer_alloc() to reflect the more traditional alloc/free symmetry. Signed-off-by:
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Peter Hurley authored
Factor shared code; prepare for adding 0-sized sentinel flip buffer. Signed-off-by:
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Peter Hurley authored
Since flip buffers are size-aligned to 256 bytes and all flip buffers 512-bytes or larger are not added to the free list, the free list only contains 256-byte flip buffers. Remove the list search when allocating a new flip buffer. Signed-off-by:
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Peter Hurley authored
The char_buf_ptr and flag_buf_ptr values are trivially derived from the .data field offset; compute values as needed. Fixes a long-standing type-mismatch with the char and flag ptrs. Signed-off-by:
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Peter Hurley authored
Scheduling buffer work on the same cpu as the read() thread limits the parallelism now possible between the receive_buf path and the n_tty_read() path. Signed-off-by:
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Peter Hurley authored
The pty driver forces ldisc flow control on, regardless of available receive buffer space, so the writer can be woken whenever unthrottle is called. However, this 'forced throttle' has performance consequences, as multiple atomic operations are necessary to unthrottle and perform the write wakeup for every input line (in canonical mode). Instead, short-circuit the unthrottle if the tty is a pty and perform the write wakeup directly. Signed-off-by:
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Peter Hurley authored
Prepare to special case pty flow control; avoid forward declaration. Signed-off-by:
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Peter Hurley authored
Prepare for special handling of pty throttle/unthrottle; factor flow control into helper functions. Signed-off-by:
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Peter Hurley authored
Prepare to factor throttle and unthrottle into helper functions; relocate chars_in_buffer() to avoid forward declaration. Signed-off-by:
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Peter Hurley authored
No tty driver modifies termios during throttle() or unthrottle(). Therefore, only read safety is required. However, tty_throttle_safe and tty_unthrottle_safe must still be mutually exclusive; introduce throttle_mutex for that purpose. Signed-off-by:
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Peter Hurley authored
If the read buffer indices are in the same cache-line, cpus will contended over the cache-line (so called 'false sharing'). Separate the producer-published fields from the consumer-published fields; document the locks relevant to each field. Signed-off-by:
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Peter Hurley authored
User-space read() can run concurrently with receiving from device; waiting for receive_buf() to complete is not required. Signed-off-by:
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Peter Hurley authored
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Peter Hurley authored
lnext escapes the next input character as a literal, and must be reset when canonical mode changes (to avoid misinterpreting a special character as a literal if canonical mode is changed back again). lnext is specifically not reset on a buffer flush so as to avoid misinterpreting the next input character as a special character. Signed-off-by:
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Peter Hurley authored
n_tty has a single-producer/single-consumer input model; use lockless publish instead. Use termios_rwsem to exclude both consumer and producer while changing or resetting buffer indices, eg., when flushing. Also, claim exclusive termios_rwsem to safely retrieve the buffer indices from a thread other than consumer or producer (eg., TIOCINQ ioctl). Note the read_tail is published _after_ clearing the newline indicator in read_flags to avoid racing the producer. Drop read_lock spinlock. Signed-off-by:
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Peter Hurley authored
canon_data represented the # of lines which had been copied to the receive buffer but not yet copied to the user buffer. The value was tested to determine if input was available in canonical mode (and also to force input overrun if the receive buffer was full but a newline had not been received). However, the actual count was irrelevent; only whether it was non-zero (meaning 'is there any input to transfer?'). This shared count is unnecessary and unsafe with a lockless algorithm. The same check is made by comparing canon_head with read_tail instead. Signed-off-by:
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Peter Hurley authored
Use termios_rwsem to guarantee safe access to the termios values. This is particularly important for N_TTY as changing certain termios settings alters the mode of operation. termios_rwsem must be dropped across throttle/unthrottle since those functions claim the termios_rwsem exclusively (to guarantee safe access to the termios and for mutual exclusion). Signed-off-by:
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Peter Hurley authored
termios is commonly accessed unsafely (especially by N_TTY) because the existing mutex forces exclusive access. Convert existing usage. Signed-off-by:
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Peter Hurley authored
Storing the read_cnt creates an unnecessary shared variable between the single-producer (n_tty_receive_buf()) and the single-consumer (n_tty_read()). Compute read_cnt from head & tail instead of storing. Signed-off-by:
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Peter Hurley authored
Wrap read_buf indices (read_head, read_tail, canon_head) at max representable value, instead of at the N_TTY_BUF_SIZE. This step is necessary to allow lockless reads of these shared variables (by updating the variables atomically). Signed-off-by:
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Peter Hurley authored
Prepare for replacing read_cnt field with computed value. Signed-off-by:
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Peter Hurley authored
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Peter Hurley authored
N_TTY .chars_in_buffer() method requires serialized access if the current thread is not the single-consumer, n_tty_read(). Separate the internal interface; prepare for lockless read-side. Signed-off-by:
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Peter Hurley authored
Instead of pushing one char per loop, pre-compute the data length to copy and copy all at once. Signed-off-by:
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Peter Hurley authored
Simplify n_tty_read(); extract complex copy algorithm into separate function, canon_copy_to_user(). Signed-off-by:
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Peter Hurley authored
Although line discipline receiving is single-producer/single-consumer, using tty->receive_room to manage flow control creates unnecessary critical regions requiring additional lock use. Instead, introduce the optional .receive_buf2() ldisc method which returns the # of bytes actually received. Serialization is guaranteed by the caller. In turn, the line discipline should schedule the buffer work item whenever space becomes available; ie., when there is room to receive data and receive_room() previously returned 0 (the buffer work item stops processing if receive_buf2() returns 0). Note the 'no room' state need not be atomic despite concurrent use by two threads because only the buffer work thread can set the state and only the read() thread can clear the state. Add n_tty_receive_buf2() as the receive_buf2() method for N_TTY. Provide a public helper function, tty_ldisc_receive_buf(), to use when directly accessing the receive_buf() methods. Line disciplines not using input flow control can continue to set tty->receive_room to a fixed value and only provide the receive_buf() method. Signed-off-by:
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Peter Hurley authored
Ldisc interface functions must be called with interrupts enabled. Separating the ldisc calls into a helper function simplies the eventual removal of the spinlock. Note that access to the buf->head ptr outside the spinlock is safe here because; * __tty_buffer_flush() is prevented from running while buffer work performs i/o, * tty_buffer_find() only assigns buf->head if the flip buffer list is empty (which is never the case in flush_to_ldisc() since at least one buffer is always left in the list after use) Access to the read index outside the spinlock is safe here for the same reasons. Update the buffer's read index _after_ the data has been received by the ldisc. Signed-off-by:
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Peter Hurley authored
tty_set_ldisc() is guaranteed exclusive use of the line discipline by tty_ldisc_lock_pair_timeout(); shutting off input by resetting receive_room is unnecessary. Signed-off-by:
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Peter Hurley authored
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Peter Hurley authored
The hangup may already have happened; check for that state also. Signed-off-by:
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Peter Hurley authored
Rename o_ldisc to avoid confusion with the ldisc of the 'other' tty. Signed-off-by:
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Peter Hurley authored
Line discipline locking was performed with a combination of a mutex, a status bit, a count, and a waitqueue -- basically, a rw semaphore. Replace the existing combination with an ld_semaphore. Fixes: 1) the 'reference acquire after ldisc locked' bug 2) the over-complicated halt mechanism 3) lock order wrt. tty_lock() 4) dropping locks while changing ldisc 5) previously unidentified deadlock while locking ldisc from both linked ttys concurrently 6) previously unidentified recursive deadlocks Adds much-needed lockdep diagnostics. Signed-off-by: -
Peter Hurley authored
Just as the tty pair must be locked in a stable sequence (ie, independent of which is consider the 'other' tty), so must the ldisc pair be locked in a stable sequence as well. Signed-off-by:
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Peter Hurley authored
The file scope spinlock identifier, tty_ldisc_lock, will collide with the file scope lock function tty_ldisc_lock() so rename it. Signed-off-by:
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- 21 Jul, 2013 5 commits
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Linus Torvalds authored
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git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pmLinus Torvalds authored
Pull ACPI video support fixes from Rafael Wysocki: "I'm sending a separate pull request for this as it may be somewhat controversial. The breakage addressed here is not really new and the fixes may not satisfy all users of the affected systems, but we've had so much back and forth dance in this area over the last several weeks that I think it's time to actually make some progress. The source of the problem is that about a year ago we started to tell BIOSes that we're compatible with Windows 8, which we really need to do, because some systems shipping with Windows 8 are tested with it and nothing else, so if we tell their BIOSes that we aren't compatible with Windows 8, we expose our users to untested BIOS/AML code paths. However, as it turns out, some Windows 8-specific AML code paths are not tested either, because Windows 8 actually doesn't use the ACPI methods containing them, so if we declare Windows 8 compatibility and attempt to use those ACPI methods, things break. That occurs mostly in the backlight support area where in particular the _BCM and _BQC methods are plain unusable on some systems if the OS declares Windows 8 compatibility. [ The additional twist is that they actually become usable if the OS says it is not compatible with Windows 8, but that may cause problems to show up elsewhere ] Investigation carried out by Matthew Garrett indicates that what Windows 8 does about backlight is to leave backlight control up to individual graphics drivers. At least there's evidence that it does that if the Intel graphics driver is used, so we've decided to follow Windows 8 in that respect and allow i915 to control backlight (Daniel likes that part). The first commit from Aaron Lu makes ACPICA export the variable from which we can infer whether or not the BIOS believes that we are compatible with Windows 8. The second commit from Matthew Garrett prepares the ACPI video driver by making it initialize the ACPI backlight even if it is not going to be used afterward (that is needed for backlight control to work on Thinkpads). The third commit implements the actual workaround making i915 take over backlight control if the firmware thinks it's dealing with Windows 8 and is based on the work of multiple developers, including Matthew Garrett, Chun-Yi Lee, Seth Forshee, and Aaron Lu. The final commit from Aaron Lu makes us follow Windows 8 by informing the firmware through the _DOS method that it should not carry out automatic brightness changes, so that brightness can be controlled by GUI. Hopefully, this approach will allow us to avoid using blacklists of systems that should not declare Windows 8 compatibility just to avoid backlight control problems in the future. - Change from Aaron Lu makes ACPICA export a variable which can be used by driver code to determine whether or not the BIOS believes that we are compatible with Windows 8. - Change from Matthew Garrett makes the ACPI video driver initialize the ACPI backlight even if it is not going to be used afterward (that is needed for backlight control to work on Thinkpads). - Fix from Rafael J Wysocki implements Windows 8 backlight support workaround making i915 take over bakclight control if the firmware thinks it's dealing with Windows 8. Based on the work of multiple developers including Matthew Garrett, Chun-Yi Lee, Seth Forshee, and Aaron Lu. - Fix from Aaron Lu makes the kernel follow Windows 8 by informing the firmware through the _DOS method that it should not carry out automatic brightness changes, so that brightness can be controlled by GUI" * tag 'acpi-video-3.11' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: ACPI / video: no automatic brightness changes by win8-compatible firmware ACPI / video / i915: No ACPI backlight if firmware expects Windows 8 ACPI / video: Always call acpi_video_init_brightness() on init ACPICA: expose OSI version -
git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4Linus Torvalds authored
Pull ext[34] tmpfile bugfix from Ted Ts'o: "Fix regression caused by commit af51a2ac which added ->tmpfile() support (along with a similar fix for ext3)" * tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: ext3: fix a BUG when opening a file with O_TMPFILE flag ext4: fix a BUG when opening a file with O_TMPFILE flag
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Zheng Liu authored
When we try to open a file with O_TMPFILE flag, we will trigger a bug. The root cause is that in ext4_orphan_add() we check ->i_nlink == 0 and this check always fails because we set ->i_nlink = 1 in inode_init_always(). We can use the following program to trigger it: int main(int argc, char *argv[]) { int fd; fd = open(argv[1], O_TMPFILE, 0666); if (fd < 0) { perror("open "); return -1; } close(fd); return 0; } The oops message looks like this: kernel: kernel BUG at fs/ext3/namei.c:1992! kernel: invalid opcode: 0000 [#1] SMP kernel: Modules linked in: ext4 jbd2 crc16 cpufreq_ondemand ipv6 dm_mirror dm_region_hash dm_log dm_mod parport_pc parport serio_raw sg dcdbas pcspkr i2c_i801 ehci_pci ehci_hcd button acpi_cpufreq mperf e1000e ptp pps_core ttm drm_kms_helper drm hwmon i2c_algo_bit i2c_core ext3 jbd sd_mod ahci libahci libata scsi_mod uhci_hcd kernel: CPU: 0 PID: 2882 Comm: tst_tmpfile Not tainted 3.11.0-rc1+ #4 kernel: Hardware name: Dell Inc. OptiPlex 780 /0V4W66, BIOS A05 08/11/2010 kernel: task: ffff880112d30050 ti: ffff8801124d4000 task.ti: ffff8801124d4000 kernel: RIP: 0010:[<ffffffffa00db5ae>] [<ffffffffa00db5ae>] ext3_orphan_add+0x6a/0x1eb [ext3] kernel: RSP: 0018:ffff8801124d5cc8 EFLAGS: 00010202 kernel: RAX: 0000000000000000 RBX: ffff880111510128 RCX: ffff8801114683a0 kernel: RDX: 0000000000000000 RSI: ffff880111510128 RDI: ffff88010fcf65a8 kernel: RBP: ffff8801124d5d18 R08: 0080000000000000 R09: ffffffffa00d3b7f kernel: R10: ffff8801114683a0 R11: ffff8801032a2558 R12: 0000000000000000 kernel: R13: ffff88010fcf6800 R14: ffff8801032a2558 R15: ffff8801115100d8 kernel: FS: 00007f5d172b5700(0000) GS:ffff880117c00000(0000) knlGS:0000000000000000 kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b kernel: CR2: 00007f5d16df15d0 CR3: 0000000110b1d000 CR4: 00000000000407f0 kernel: Stack: kernel: 000000000000000c ffff8801048a7dc8 ffff8801114685a8 ffffffffa00b80d7 kernel: ffff8801124d5e38 ffff8801032a2558 ffff88010ce24d68 0000000000000000 kernel: ffff88011146b300 ffff8801124d5d44 ffff8801124d5d78 ffffffffa00db7e1 kernel: Call Trace: kernel: [<ffffffffa00b80d7>] ? journal_start+0x8c/0xbd [jbd] kernel: [<ffffffffa00db7e1>] ext3_tmpfile+0xb2/0x13b [ext3] kernel: [<ffffffff821076f8>] path_openat+0x11f/0x5e7 kernel: [<ffffffff821c86b4>] ? list_del+0x11/0x30 kernel: [<ffffffff82065fa2>] ? __dequeue_entity+0x33/0x38 kernel: [<ffffffff82107cd5>] do_filp_open+0x3f/0x8d kernel: [<ffffffff82112532>] ? __alloc_fd+0x50/0x102 kernel: [<ffffffff820f9296>] do_sys_open+0x13b/0x1cd kernel: [<ffffffff820f935c>] SyS_open+0x1e/0x20 kernel: [<ffffffff82398c02>] system_call_fastpath+0x16/0x1b kernel: Code: 39 c7 0f 85 67 01 00 00 0f b7 03 25 00 f0 00 00 3d 00 40 00 00 74 18 3d 00 80 00 00 74 11 3d 00 a0 00 00 74 0a 83 7b 48 00 74 04 <0f> 0b eb fe 49 8b 85 50 03 00 00 4c 89 f6 48 c7 c7 c0 99 0e a0 kernel: RIP [<ffffffffa00db5ae>] ext3_orphan_add+0x6a/0x1eb [ext3] kernel: RSP <ffff8801124d5cc8> Here we couldn't call clear_nlink() directly because in d_tmpfile() we will call inode_dec_link_count() to decrease ->i_nlink. So this commit tries to call d_tmpfile() before ext4_orphan_add() to fix this problem. Signed-off-by:Zheng Liu <wenqing.lz@taobao.com> Signed-off-by:
"Theodore Ts'o" <tytso@mit.edu> Cc: Jan Kara <jack@suse.cz> Cc: Al Viro <viro@zeniv.linux.org.uk>
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Zheng Liu authored
When we try to open a file with O_TMPFILE flag, we will trigger a bug. The root cause is that in ext4_orphan_add() we check ->i_nlink == 0 and this check always fails because we set ->i_nlink = 1 in inode_init_always(). We can use the following program to trigger it: int main(int argc, char *argv[]) { int fd; fd = open(argv[1], O_TMPFILE, 0666); if (fd < 0) { perror("open "); return -1; } close(fd); return 0; } The oops message looks like this: kernel BUG at fs/ext4/namei.c:2572! invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC Modules linked in: dlci bridge stp hidp cmtp kernelcapi l2tp_ppp l2tp_netlink l2tp_core sctp libcrc32c rfcomm tun fuse nfnetli nk can_raw ipt_ULOG can_bcm x25 scsi_transport_iscsi ipx p8023 p8022 appletalk phonet psnap vmw_vsock_vmci_transport af_key vmw_vmci rose vsock atm can netrom ax25 af_rxrpc ir da pppoe pppox ppp_generic slhc bluetooth nfc rfkill rds caif_socket caif crc_ccitt af_802154 llc2 llc snd_hda_codec_realtek snd_hda_intel snd_hda_codec serio_raw snd_pcm pcsp kr edac_core snd_page_alloc snd_timer snd soundcore r8169 mii sr_mod cdrom pata_atiixp radeon backlight drm_kms_helper ttm CPU: 1 PID: 1812571 Comm: trinity-child2 Not tainted 3.11.0-rc1+ #12 Hardware name: Gigabyte Technology Co., Ltd. GA-MA78GM-S2H/GA-MA78GM-S2H, BIOS F12a 04/23/2010 task: ffff88007dfe69a0 ti: ffff88010f7b6000 task.ti: ffff88010f7b6000 RIP: 0010:[<ffffffff8125ce69>] [<ffffffff8125ce69>] ext4_orphan_add+0x299/0x2b0 RSP: 0018:ffff88010f7b7cf8 EFLAGS: 00010202 RAX: 0000000000000000 RBX: ffff8800966d3020 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff88007dfe70b8 RDI: 0000000000000001 RBP: ffff88010f7b7d40 R08: ffff880126a3c4e0 R09: ffff88010f7b7ca0 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801271fd668 R13: ffff8800966d2f78 R14: ffff88011d7089f0 R15: ffff88007dfe69a0 FS: 00007f70441a3740(0000) GS:ffff88012a800000(0000) knlGS:00000000f77c96c0 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000002834000 CR3: 0000000107964000 CR4: 00000000000007e0 DR0: 0000000000780000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 Stack: 0000000000002000 00000020810b6dde 0000000000000000 ffff88011d46db00 ffff8800966d3020 ffff88011d7089f0 ffff88009c7f4c10 ffff88010f7b7f2c ffff88007dfe69a0 ffff88010f7b7da8 ffffffff8125cfac ffff880100000004 Call Trace: [<ffffffff8125cfac>] ext4_tmpfile+0x12c/0x180 [<ffffffff811cba78>] path_openat+0x238/0x700 [<ffffffff8100afc4>] ? native_sched_clock+0x24/0x80 [<ffffffff811cc647>] do_filp_open+0x47/0xa0 [<ffffffff811db73f>] ? __alloc_fd+0xaf/0x200 [<ffffffff811ba2e4>] do_sys_open+0x124/0x210 [<ffffffff81010725>] ? syscall_trace_enter+0x25/0x290 [<ffffffff811ba3ee>] SyS_open+0x1e/0x20 [<ffffffff816ca8d4>] tracesys+0xdd/0xe2 [<ffffffff81001001>] ? start_thread_common.constprop.6+0x1/0xa0 Code: 04 00 00 00 89 04 24 31 c0 e8 c4 77 04 00 e9 43 fe ff ff 66 25 00 d0 66 3d 00 80 0f 84 0e fe ff ff 83 7b 48 00 0f 84 04 fe ff ff <0f> 0b 49 8b 8c 24 50 07 00 00 e9 88 fe ff ff 0f 1f 84 00 00 00 Here we couldn't call clear_nlink() directly because in d_tmpfile() we will call inode_dec_link_count() to decrease ->i_nlink. So this commit tries to call d_tmpfile() before ext4_orphan_add() to fix this problem. Reported-by:Dave Jones <davej@redhat.com> Signed-off-by:
Darrick J. Wong <darrick.wong@oracle.com> Tested-by:
Al Viro <viro@zeniv.linux.org.uk>
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