The patch titled
revert "pty: Rework the pty layer to use the normal buffering logic"
has been removed from the -mm tree. Its filename was
revert-pty-rework-the-pty-layer-to-use-the-normal-buffering-logic.patch
This patch was dropped because it was withdrawn
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: revert "pty: Rework the pty layer to use the normal buffering logic"
From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Revert
: commit d945cb9cce20ac7143c2de8d88b187f62db99bdc
: Author: Alan Cox <alan@xxxxxxxxxxxxxxx>
: AuthorDate: Tue Jul 7 16:39:41 2009 +0100
: Commit: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
: CommitDate: Wed Jul 8 09:47:59 2009 -0700
:
: pty: Rework the pty layer to use the normal buffering logic
Due to http://bugzilla.kernel.org/show_bug.cgi?id=13815
Reported-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/char/pty.c | 152 ++++++++++++++++++++++++++-----------------
1 file changed, 94 insertions(+), 58 deletions(-)
diff -puN drivers/char/pty.c~revert-pty-rework-the-pty-layer-to-use-the-normal-buffering-logic drivers/char/pty.c
--- a/drivers/char/pty.c~revert-pty-rework-the-pty-layer-to-use-the-normal-buffering-logic
+++ a/drivers/char/pty.c
@@ -76,88 +76,114 @@ static void pty_close(struct tty_struct
*/
static void pty_unthrottle(struct tty_struct *tty)
{
- tty_wakeup(tty->link);
- set_bit(TTY_THROTTLED, &tty->flags);
-}
+ struct tty_struct *o_tty = tty->link;
-/**
- * pty_space - report space left for writing
- * @to: tty we are writing into
- *
- * The tty buffers allow 64K but we sneak a peak and clip at 8K this
- * allows a lot of overspill room for echo and other fun messes to
- * be handled properly
- */
+ if (!o_tty)
+ return;
-static int pty_space(struct tty_struct *to)
-{
- int n = 8192 - to->buf.memory_used;
- if (n < 0)
- return 0;
- return n;
+ tty_wakeup(o_tty);
+ set_bit(TTY_THROTTLED, &tty->flags);
}
-/**
- * pty_write - write to a pty
- * @tty: the tty we write from
- * @buf: kernel buffer of data
- * @count: bytes to write
+/*
+ * WSH 05/24/97: modified to
+ * (1) use space in tty->flip instead of a shared temp buffer
+ * The flip buffers aren't being used for a pty, so there's lots
+ * of space available. The buffer is protected by a per-pty
+ * semaphore that should almost never come under contention.
+ * (2) avoid redundant copying for cases where count >> receive_room
+ * N.B. Calls from user space may now return an error code instead of
+ * a count.
+ *
+ * FIXME: Our pty_write method is called with our ldisc lock held but
+ * not our partners. We can't just wait on the other one blindly without
+ * risking deadlocks. At some point when everything has settled down we need
+ * to look into making pty_write at least able to sleep over an ldisc change.
*
- * Our "hardware" write method. Data is coming from the ldisc which
- * may be in a non sleeping state. We simply throw this at the other
- * end of the link as if we were an IRQ handler receiving stuff for
- * the other side of the pty/tty pair.
+ * The return on no ldisc is a bit counter intuitive but the logic works
+ * like this. During an ldisc change the other end will flush its buffers. We
+ * thus return the full length which is identical to the case where we had
+ * proper locking and happened to queue the bytes just before the flush during
+ * the ldisc change.
*/
-
static int pty_write(struct tty_struct *tty, const unsigned char *buf,
int count)
{
struct tty_struct *to = tty->link;
- int c;
+ struct tty_ldisc *ld;
+ int c = count;
- if (tty->stopped)
+ if (!to || tty->stopped)
return 0;
+ ld = tty_ldisc_ref(to);
- /* This isn't locked but our 8K is quite sloppy so no
- big deal */
-
- c = pty_space(to);
- if (c > count)
- c = count;
- if (c > 0) {
- /* Stuff the data into the input queue of the other end */
- c = tty_insert_flip_string(to, buf, c);
- /* And shovel */
- tty_flip_buffer_push(to);
- tty_wakeup(tty);
+ if (ld) {
+ c = to->receive_room;
+ if (c > count)
+ c = count;
+ ld->ops->receive_buf(to, buf, NULL, c);
+ tty_ldisc_deref(ld);
}
return c;
}
-/**
- * pty_write_room - write space
- * @tty: tty we are writing from
- *
- * Report how many bytes the ldisc can send into the queue for
- * the other device.
- */
-
static int pty_write_room(struct tty_struct *tty)
{
- return pty_space(tty->link);
+ struct tty_struct *to = tty->link;
+
+ if (!to || tty->stopped)
+ return 0;
+
+ return to->receive_room;
}
-/**
- * pty_chars_in_buffer - characters currently in our tx queue
- * @tty: our tty
+/*
+ * WSH 05/24/97: Modified for asymmetric MASTER/SLAVE behavior
+ * The chars_in_buffer() value is used by the ldisc select() function
+ * to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).
+ * The pty driver chars_in_buffer() Master/Slave must behave differently:
*
- * Report how much we have in the transmit queue. As everything is
- * instantly at the other end this is easy to implement.
+ * The Master side needs to allow typed-ahead commands to accumulate
+ * while being canonicalized, so we report "our buffer" as empty until
+ * some threshold is reached, and then report the count. (Any count >
+ * WAKEUP_CHARS is regarded by select() as "full".) To avoid deadlock
+ * the count returned must be 0 if no canonical data is available to be
+ * read. (The N_TTY ldisc.chars_in_buffer now knows this.)
+ *
+ * The Slave side passes all characters in raw mode to the Master side's
+ * buffer where they can be read immediately, so in this case we can
+ * return the true count in the buffer.
*/
-
static int pty_chars_in_buffer(struct tty_struct *tty)
{
- return 0;
+ struct tty_struct *to = tty->link;
+ struct tty_ldisc *ld;
+ int count = 0;
+
+ /* We should get the line discipline lock for "tty->link" */
+ if (!to)
+ return 0;
+ /* We cannot take a sleeping reference here without deadlocking with
+ an ldisc change - but it doesn't really matter */
+ ld = tty_ldisc_ref(to);
+ if (ld == NULL)
+ return 0;
+
+ /* The ldisc must report 0 if no characters available to be read */
+ if (ld->ops->chars_in_buffer)
+ count = ld->ops->chars_in_buffer(to);
+
+ tty_ldisc_deref(ld);
+
+ if (tty->driver->subtype == PTY_TYPE_SLAVE)
+ return count;
+
+ /* Master side driver ... if the other side's read buffer is less than
+ * half full, return 0 to allow writers to proceed; otherwise return
+ * the count. This leaves a comfortable margin to avoid overflow,
+ * and still allows half a buffer's worth of typed-ahead commands.
+ */
+ return (count < N_TTY_BUF_SIZE/2) ? 0 : count;
}
/* Set the lock flag on a pty */
@@ -177,10 +203,20 @@ static void pty_flush_buffer(struct tty_
{
struct tty_struct *to = tty->link;
unsigned long flags;
+ struct tty_ldisc *ld;
if (!to)
return;
- /* tty_buffer_flush(to); FIXME */
+ ld = tty_ldisc_ref(to);
+
+ /* The other end is changing discipline */
+ if (!ld)
+ return;
+
+ if (ld->ops->flush_buffer)
+ to->ldisc->ops->flush_buffer(to);
+ tty_ldisc_deref(ld);
+
if (to->packet) {
spin_lock_irqsave(&tty->ctrl_lock, flags);
tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
_
Patches currently in -mm which might be from akpm@xxxxxxxxxxxxxxxxxxxx are
linux-next.patch
next-remove-localversion.patch
i-need-old-gcc.patch
revert-pty-rework-the-pty-layer-to-use-the-normal-buffering-logic.patch
arch-x86-kernel-cpu-amdc-fix-x86_64-allnoconfig-build.patch
arch-x86-kernel-cpu-cpufreq-acpi-cpufreqc-avoid-cross-cpu-interrupts-by-using-smp_call_function_any.patch
arch-x86-kernel-tscc-smi-workaround-for-pit_expect_msb-checkpatch-fixes.patch
x86-add-reboot-fixup-for-compulab-sbc-fitpc2-board-cleanup.patch
platform_device_add_data-use-kmemdup.patch
drivers-pci-intel-iommuc-return-early-if-all-dmar-hw-unit-ignored-checkpatch-fixes.patch
timer-stats-fix-del_timer_sync-and-try_to_del_timer_sync.patch
input-drivers-input-xpadc-improve-xbox-360-wireless-support-and-add-sysfs-interface.patch
input-documentation-input-xpadtxt-update-for-new-driver-functionality.patch
leds-gpio-leds-fix-typographics-fault-checkpatch-fixes.patch
leds-fix-coding-style-in-worker-thread-code-for-ledtrig-gpio-checkpatch-fixes.patch
slram-read-buffer-overflow-cleanup.patch
proc-connector-add-event-for-process-becoming-session-leader.patch
3x59x-fix-pci-resource-management-checkpatch-fixes.patch
bluetooth-fix-for-acer-bluetooth-optical-rechargeable-mouse-fix.patch
scsi-make-scsi-sg-v4-driver-enabled-by-default-and-remove-experimental-dependency-since-udev-depends-on-bsg-checkpatch-fixes.patch
drivers-usb-gadget-s3c2410_udcc-fix.patch
raw-fix-rawctl-compat-ioctls-breakage-on-amd64-and-itanic.patch
libfs-make-simple_read_from_buffer-conventional.patch
fs-fix-overflow-in-sys_mount-for-in-kernel-calls-fix.patch
vfs-optimize-touch_time-too-fix.patch
watchdog-add-sbc-fitpc2-watchdog-driver-fix.patch
mm-make-set_mempolicympol_interleav-n_high_memory-aware-fix.patch
revert-mm-prevent-balance_dirty_pages-from-doing-too-much-work.patch
mm-make-swap-token-dummies-static-inlines-fix.patch
readahead-add-blk_run_backing_dev-fix.patch
readahead-add-blk_run_backing_dev-fix-fix-2.patch
memory-hotplug-update-zone-pcp-at-memory-online-fix.patch
vmscan-dont-attempt-to-reclaim-anon-page-in-lumpy-reclaim-when-no-swap-space-is-avilable.patch
ummunotify-userspace-support-for-mmu-notifications.patch
frv-duplicate-output_buffer-of-e03-checkpatch-fixes.patch
m68k-count-can-reach-51-not-50.patch
arch-m68k-include-asm-motorola_pgalloch-fix-kunmap-arg.patch
printk-boot_delay-rename-printk_delay_msec-to-loops_per_msec-fix.patch
printk-add-printk_delay-to-make-messages-readable-for-some-scenarios-fix.patch
printk-add-printk_delay-to-make-messages-readable-for-some-scenarios-cleanup.patch
generic-ipi-make-struct-call_function_data-lockless-cleanup.patch
kernel-smpc-relocate-some-code.patch
mmc-register-mmci-omap-hs-using-platform_driver_probe.patch
sdio-add-cd-disable-support-cleanup.patch
procfs-provide-stack-information-for-threads-v011-fix.patch
rtc-add-driver-for-mxcs-internal-rtc-module-fix.patch
rtc-add-driver-for-mxcs-internal-rtc-module-fix-fix.patch
rtc-philips-nxp-pcf2123-driver-v03-fix.patch
davinci-fb-frame-buffer-driver-for-ti-da8xx-omap-l1xx.patch
davinci-fb-frame-buffer-driver-for-ti-da8xx-omap-l1xx-v4-cleanup.patch
drivers-video-add-kmalloc-null-tests-fix.patch
v3-minixfs-add-missing-directory-type-checking-checkpatch-fixes.patch
memcg-remove-the-overhead-associated-with-the-root-cgroup-fix.patch
memcg-add-comments-explaining-memory-barriers-checkpatch-fixes.patch
memory-controller-soft-limit-reclaim-on-contention-v9-fix.patch
exec-make-do_coredump-more-resilient-to-recursive-crashes-v9-checkpatch-fixes.patch
exec-let-do_coredump-limit-the-number-of-concurrent-dumps-to-pipes-v9-checkpatch-fixes.patch
elf-clean-up-fill_note_info-fix.patch
net-netfilter-ipvs-ip_vs_wrrc-use-lib-gcdc-fix.patch
reiser4-export-remove_from_page_cache-fix.patch
reiser4.patch
reiser4-remove-simple_prepare_write-usage-checkpatch-fixes.patch
fs-reiser4-contextc-current_is_pdflush-got-removed.patch
slab-leaks3-default-y.patch
put_bh-debug.patch
getblk-handle-2tb-devices.patch
getblk-handle-2tb-devices-fix.patch
undeprecate-pci_find_device.patch
notify_change-callers-must-hold-i_mutex.patch
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