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6b9dbedbe3
pty_write() invokes kmalloc() which may invoke a normal printk() to print failure message. This can cause a deadlock in the scenario reported by syz-bot below: CPU0 CPU1 CPU2 ---- ---- ---- lock(console_owner); lock(&port_lock_key); lock(&port->lock); lock(&port_lock_key); lock(&port->lock); lock(console_owner); As commitdbdda842fe
("printk: Add console owner and waiter logic to load balance console writes") said, such deadlock can be prevented by using printk_deferred() in kmalloc() (which is invoked in the section guarded by the port->lock). But there are too many printk() on the kmalloc() path, and kmalloc() can be called from anywhere, so changing printk() to printk_deferred() is too complicated and inelegant. Therefore, this patch chooses to specify __GFP_NOWARN to kmalloc(), so that printk() will not be called, and this deadlock problem can be avoided. Syzbot reported the following lockdep error: ====================================================== WARNING: possible circular locking dependency detected 5.4.143-00237-g08ccc19a-dirty #10 Not tainted ------------------------------------------------------ syz-executor.4/29420 is trying to acquire lock: ffffffff8aedb2a0 (console_owner){....}-{0:0}, at: console_trylock_spinning kernel/printk/printk.c:1752 [inline] ffffffff8aedb2a0 (console_owner){....}-{0:0}, at: vprintk_emit+0x2ca/0x470 kernel/printk/printk.c:2023 but task is already holding lock: ffff8880119c9158 (&port->lock){-.-.}-{2:2}, at: pty_write+0xf4/0x1f0 drivers/tty/pty.c:120 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&port->lock){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x35/0x50 kernel/locking/spinlock.c:159 tty_port_tty_get drivers/tty/tty_port.c:288 [inline] <-- lock(&port->lock); tty_port_default_wakeup+0x1d/0xb0 drivers/tty/tty_port.c:47 serial8250_tx_chars+0x530/0xa80 drivers/tty/serial/8250/8250_port.c:1767 serial8250_handle_irq.part.0+0x31f/0x3d0 drivers/tty/serial/8250/8250_port.c:1854 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1827 [inline] <-- lock(&port_lock_key); serial8250_default_handle_irq+0xb2/0x220 drivers/tty/serial/8250/8250_port.c:1870 serial8250_interrupt+0xfd/0x200 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x109/0xa50 kernel/irq/handle.c:156 [...] -> #1 (&port_lock_key){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x35/0x50 kernel/locking/spinlock.c:159 serial8250_console_write+0x184/0xa40 drivers/tty/serial/8250/8250_port.c:3198 <-- lock(&port_lock_key); call_console_drivers kernel/printk/printk.c:1819 [inline] console_unlock+0x8cb/0xd00 kernel/printk/printk.c:2504 vprintk_emit+0x1b5/0x470 kernel/printk/printk.c:2024 <-- lock(console_owner); vprintk_func+0x8d/0x250 kernel/printk/printk_safe.c:394 printk+0xba/0xed kernel/printk/printk.c:2084 register_console+0x8b3/0xc10 kernel/printk/printk.c:2829 univ8250_console_init+0x3a/0x46 drivers/tty/serial/8250/8250_core.c:681 console_init+0x49d/0x6d3 kernel/printk/printk.c:2915 start_kernel+0x5e9/0x879 init/main.c:713 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241 -> #0 (console_owner){....}-{0:0}: [...] lock_acquire+0x127/0x340 kernel/locking/lockdep.c:4734 console_trylock_spinning kernel/printk/printk.c:1773 [inline] <-- lock(console_owner); vprintk_emit+0x307/0x470 kernel/printk/printk.c:2023 vprintk_func+0x8d/0x250 kernel/printk/printk_safe.c:394 printk+0xba/0xed kernel/printk/printk.c:2084 fail_dump lib/fault-inject.c:45 [inline] should_fail+0x67b/0x7c0 lib/fault-inject.c:144 __should_failslab+0x152/0x1c0 mm/failslab.c:33 should_failslab+0x5/0x10 mm/slab_common.c:1224 slab_pre_alloc_hook mm/slab.h:468 [inline] slab_alloc_node mm/slub.c:2723 [inline] slab_alloc mm/slub.c:2807 [inline] __kmalloc+0x72/0x300 mm/slub.c:3871 kmalloc include/linux/slab.h:582 [inline] tty_buffer_alloc+0x23f/0x2a0 drivers/tty/tty_buffer.c:175 __tty_buffer_request_room+0x156/0x2a0 drivers/tty/tty_buffer.c:273 tty_insert_flip_string_fixed_flag+0x93/0x250 drivers/tty/tty_buffer.c:318 tty_insert_flip_string include/linux/tty_flip.h:37 [inline] pty_write+0x126/0x1f0 drivers/tty/pty.c:122 <-- lock(&port->lock); n_tty_write+0xa7a/0xfc0 drivers/tty/n_tty.c:2356 do_tty_write drivers/tty/tty_io.c:961 [inline] tty_write+0x512/0x930 drivers/tty/tty_io.c:1045 __vfs_write+0x76/0x100 fs/read_write.c:494 [...] other info that might help us debug this: Chain exists of: console_owner --> &port_lock_key --> &port->lock Link: https://lkml.kernel.org/r/20220511061951.1114-2-zhengqi.arch@bytedance.com Link: https://lkml.kernel.org/r/20220510113809.80626-2-zhengqi.arch@bytedance.com Fixes:b6da31b2c0
("tty: Fix data race in tty_insert_flip_string_fixed_flag") Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> Acked-by: Jiri Slaby <jirislaby@kernel.org> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Akinobu Mita <akinobu.mita@gmail.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
618 lines
16 KiB
C
618 lines
16 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Tty buffer allocation management
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*/
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#include <linux/types.h>
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#include <linux/errno.h>
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#include <linux/tty.h>
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#include <linux/tty_driver.h>
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#include <linux/tty_flip.h>
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#include <linux/timer.h>
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#include <linux/string.h>
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#include <linux/slab.h>
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#include <linux/sched.h>
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#include <linux/wait.h>
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#include <linux/bitops.h>
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#include <linux/delay.h>
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#include <linux/module.h>
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#include <linux/ratelimit.h>
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#include "tty.h"
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#define MIN_TTYB_SIZE 256
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#define TTYB_ALIGN_MASK 255
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/*
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* Byte threshold to limit memory consumption for flip buffers.
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* The actual memory limit is > 2x this amount.
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*/
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#define TTYB_DEFAULT_MEM_LIMIT (640 * 1024UL)
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/*
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* We default to dicing tty buffer allocations to this many characters
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* in order to avoid multiple page allocations. We know the size of
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* tty_buffer itself but it must also be taken into account that the
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* buffer is 256 byte aligned. See tty_buffer_find for the allocation
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* logic this must match.
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*/
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#define TTY_BUFFER_PAGE (((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~0xFF)
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/**
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* tty_buffer_lock_exclusive - gain exclusive access to buffer
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* @port: tty port owning the flip buffer
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*
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* Guarantees safe use of the &tty_ldisc_ops.receive_buf() method by excluding
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* the buffer work and any pending flush from using the flip buffer. Data can
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* continue to be added concurrently to the flip buffer from the driver side.
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*
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* See also tty_buffer_unlock_exclusive().
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*/
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void tty_buffer_lock_exclusive(struct tty_port *port)
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{
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struct tty_bufhead *buf = &port->buf;
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atomic_inc(&buf->priority);
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mutex_lock(&buf->lock);
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}
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EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive);
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/**
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* tty_buffer_unlock_exclusive - release exclusive access
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* @port: tty port owning the flip buffer
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*
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* The buffer work is restarted if there is data in the flip buffer.
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*
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* See also tty_buffer_lock_exclusive().
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*/
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void tty_buffer_unlock_exclusive(struct tty_port *port)
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{
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struct tty_bufhead *buf = &port->buf;
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int restart;
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restart = buf->head->commit != buf->head->read;
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atomic_dec(&buf->priority);
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mutex_unlock(&buf->lock);
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if (restart)
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queue_work(system_unbound_wq, &buf->work);
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}
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EXPORT_SYMBOL_GPL(tty_buffer_unlock_exclusive);
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/**
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* tty_buffer_space_avail - return unused buffer space
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* @port: tty port owning the flip buffer
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*
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* Returns: the # of bytes which can be written by the driver without reaching
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* the buffer limit.
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*
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* Note: this does not guarantee that memory is available to write the returned
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* # of bytes (use tty_prepare_flip_string() to pre-allocate if memory
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* guarantee is required).
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*/
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unsigned int tty_buffer_space_avail(struct tty_port *port)
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{
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int space = port->buf.mem_limit - atomic_read(&port->buf.mem_used);
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return max(space, 0);
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}
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EXPORT_SYMBOL_GPL(tty_buffer_space_avail);
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static void tty_buffer_reset(struct tty_buffer *p, size_t size)
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{
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p->used = 0;
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p->size = size;
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p->next = NULL;
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p->commit = 0;
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p->read = 0;
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p->flags = 0;
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}
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/**
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* tty_buffer_free_all - free buffers used by a tty
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* @port: tty port to free from
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*
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* Remove all the buffers pending on a tty whether queued with data or in the
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* free ring. Must be called when the tty is no longer in use.
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*/
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void tty_buffer_free_all(struct tty_port *port)
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{
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struct tty_bufhead *buf = &port->buf;
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struct tty_buffer *p, *next;
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struct llist_node *llist;
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unsigned int freed = 0;
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int still_used;
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while ((p = buf->head) != NULL) {
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buf->head = p->next;
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freed += p->size;
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if (p->size > 0)
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kfree(p);
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}
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llist = llist_del_all(&buf->free);
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llist_for_each_entry_safe(p, next, llist, free)
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kfree(p);
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tty_buffer_reset(&buf->sentinel, 0);
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buf->head = &buf->sentinel;
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buf->tail = &buf->sentinel;
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still_used = atomic_xchg(&buf->mem_used, 0);
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WARN(still_used != freed, "we still have not freed %d bytes!",
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still_used - freed);
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}
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/**
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* tty_buffer_alloc - allocate a tty buffer
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* @port: tty port
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* @size: desired size (characters)
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*
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* Allocate a new tty buffer to hold the desired number of characters. We
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* round our buffers off in 256 character chunks to get better allocation
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* behaviour.
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*
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* Returns: %NULL if out of memory or the allocation would exceed the per
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* device queue.
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*/
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static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
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{
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struct llist_node *free;
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struct tty_buffer *p;
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/* Round the buffer size out */
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size = __ALIGN_MASK(size, TTYB_ALIGN_MASK);
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if (size <= MIN_TTYB_SIZE) {
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free = llist_del_first(&port->buf.free);
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if (free) {
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p = llist_entry(free, struct tty_buffer, free);
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goto found;
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}
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}
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/* Should possibly check if this fails for the largest buffer we
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* have queued and recycle that ?
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*/
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if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit)
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return NULL;
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p = kmalloc(sizeof(struct tty_buffer) + 2 * size,
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GFP_ATOMIC | __GFP_NOWARN);
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if (p == NULL)
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return NULL;
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found:
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tty_buffer_reset(p, size);
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atomic_add(size, &port->buf.mem_used);
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return p;
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}
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/**
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* tty_buffer_free - free a tty buffer
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* @port: tty port owning the buffer
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* @b: the buffer to free
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*
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* Free a tty buffer, or add it to the free list according to our internal
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* strategy.
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*/
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static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b)
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{
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struct tty_bufhead *buf = &port->buf;
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/* Dumb strategy for now - should keep some stats */
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WARN_ON(atomic_sub_return(b->size, &buf->mem_used) < 0);
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if (b->size > MIN_TTYB_SIZE)
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kfree(b);
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else if (b->size > 0)
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llist_add(&b->free, &buf->free);
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}
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/**
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* tty_buffer_flush - flush full tty buffers
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* @tty: tty to flush
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* @ld: optional ldisc ptr (must be referenced)
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*
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* Flush all the buffers containing receive data. If @ld != %NULL, flush the
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* ldisc input buffer.
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*
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* Locking: takes buffer lock to ensure single-threaded flip buffer 'consumer'.
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*/
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void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld)
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{
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struct tty_port *port = tty->port;
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struct tty_bufhead *buf = &port->buf;
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struct tty_buffer *next;
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atomic_inc(&buf->priority);
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mutex_lock(&buf->lock);
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/* paired w/ release in __tty_buffer_request_room; ensures there are
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* no pending memory accesses to the freed buffer
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*/
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while ((next = smp_load_acquire(&buf->head->next)) != NULL) {
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tty_buffer_free(port, buf->head);
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buf->head = next;
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}
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buf->head->read = buf->head->commit;
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if (ld && ld->ops->flush_buffer)
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ld->ops->flush_buffer(tty);
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atomic_dec(&buf->priority);
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mutex_unlock(&buf->lock);
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}
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/**
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* __tty_buffer_request_room - grow tty buffer if needed
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* @port: tty port
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* @size: size desired
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* @flags: buffer flags if new buffer allocated (default = 0)
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*
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* Make at least @size bytes of linear space available for the tty buffer.
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*
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* Will change over to a new buffer if the current buffer is encoded as
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* %TTY_NORMAL (so has no flags buffer) and the new buffer requires a flags
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* buffer.
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*
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* Returns: the size we managed to find.
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*/
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static int __tty_buffer_request_room(struct tty_port *port, size_t size,
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int flags)
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{
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struct tty_bufhead *buf = &port->buf;
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struct tty_buffer *b, *n;
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int left, change;
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b = buf->tail;
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if (b->flags & TTYB_NORMAL)
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left = 2 * b->size - b->used;
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else
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left = b->size - b->used;
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change = (b->flags & TTYB_NORMAL) && (~flags & TTYB_NORMAL);
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if (change || left < size) {
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/* This is the slow path - looking for new buffers to use */
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n = tty_buffer_alloc(port, size);
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if (n != NULL) {
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n->flags = flags;
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buf->tail = n;
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/* paired w/ acquire in flush_to_ldisc(); ensures
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* flush_to_ldisc() sees buffer data.
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*/
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smp_store_release(&b->commit, b->used);
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/* paired w/ acquire in flush_to_ldisc(); ensures the
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* latest commit value can be read before the head is
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* advanced to the next buffer
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*/
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smp_store_release(&b->next, n);
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} else if (change)
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size = 0;
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else
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size = left;
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}
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return size;
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}
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int tty_buffer_request_room(struct tty_port *port, size_t size)
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{
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return __tty_buffer_request_room(port, size, 0);
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}
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EXPORT_SYMBOL_GPL(tty_buffer_request_room);
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/**
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* tty_insert_flip_string_fixed_flag - add characters to the tty buffer
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* @port: tty port
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* @chars: characters
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* @flag: flag value for each character
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* @size: size
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*
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* Queue a series of bytes to the tty buffering. All the characters passed are
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* marked with the supplied flag.
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*
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* Returns: the number added.
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*/
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int tty_insert_flip_string_fixed_flag(struct tty_port *port,
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const unsigned char *chars, char flag, size_t size)
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{
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int copied = 0;
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do {
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int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
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int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0;
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int space = __tty_buffer_request_room(port, goal, flags);
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struct tty_buffer *tb = port->buf.tail;
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if (unlikely(space == 0))
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break;
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memcpy(char_buf_ptr(tb, tb->used), chars, space);
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if (~tb->flags & TTYB_NORMAL)
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memset(flag_buf_ptr(tb, tb->used), flag, space);
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tb->used += space;
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copied += space;
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chars += space;
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/* There is a small chance that we need to split the data over
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* several buffers. If this is the case we must loop.
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*/
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} while (unlikely(size > copied));
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return copied;
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}
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EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
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/**
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* tty_insert_flip_string_flags - add characters to the tty buffer
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* @port: tty port
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* @chars: characters
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* @flags: flag bytes
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* @size: size
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*
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* Queue a series of bytes to the tty buffering. For each character the flags
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* array indicates the status of the character.
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*
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* Returns: the number added.
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*/
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int tty_insert_flip_string_flags(struct tty_port *port,
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const unsigned char *chars, const char *flags, size_t size)
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{
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int copied = 0;
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do {
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int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
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int space = tty_buffer_request_room(port, goal);
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struct tty_buffer *tb = port->buf.tail;
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if (unlikely(space == 0))
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break;
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memcpy(char_buf_ptr(tb, tb->used), chars, space);
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memcpy(flag_buf_ptr(tb, tb->used), flags, space);
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tb->used += space;
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copied += space;
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chars += space;
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flags += space;
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/* There is a small chance that we need to split the data over
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* several buffers. If this is the case we must loop.
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*/
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} while (unlikely(size > copied));
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return copied;
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}
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EXPORT_SYMBOL(tty_insert_flip_string_flags);
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/**
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* __tty_insert_flip_char - add one character to the tty buffer
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* @port: tty port
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* @ch: character
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* @flag: flag byte
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*
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* Queue a single byte @ch to the tty buffering, with an optional flag. This is
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* the slow path of tty_insert_flip_char().
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*/
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int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag)
|
|
{
|
|
struct tty_buffer *tb;
|
|
int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0;
|
|
|
|
if (!__tty_buffer_request_room(port, 1, flags))
|
|
return 0;
|
|
|
|
tb = port->buf.tail;
|
|
if (~tb->flags & TTYB_NORMAL)
|
|
*flag_buf_ptr(tb, tb->used) = flag;
|
|
*char_buf_ptr(tb, tb->used++) = ch;
|
|
|
|
return 1;
|
|
}
|
|
EXPORT_SYMBOL(__tty_insert_flip_char);
|
|
|
|
/**
|
|
* tty_prepare_flip_string - make room for characters
|
|
* @port: tty port
|
|
* @chars: return pointer for character write area
|
|
* @size: desired size
|
|
*
|
|
* Prepare a block of space in the buffer for data.
|
|
*
|
|
* This is used for drivers that need their own block copy routines into the
|
|
* buffer. There is no guarantee the buffer is a DMA target!
|
|
*
|
|
* Returns: the length available and buffer pointer (@chars) to the space which
|
|
* is now allocated and accounted for as ready for normal characters.
|
|
*/
|
|
int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars,
|
|
size_t size)
|
|
{
|
|
int space = __tty_buffer_request_room(port, size, TTYB_NORMAL);
|
|
|
|
if (likely(space)) {
|
|
struct tty_buffer *tb = port->buf.tail;
|
|
|
|
*chars = char_buf_ptr(tb, tb->used);
|
|
if (~tb->flags & TTYB_NORMAL)
|
|
memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space);
|
|
tb->used += space;
|
|
}
|
|
return space;
|
|
}
|
|
EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
|
|
|
|
/**
|
|
* tty_ldisc_receive_buf - forward data to line discipline
|
|
* @ld: line discipline to process input
|
|
* @p: char buffer
|
|
* @f: %TTY_NORMAL, %TTY_BREAK, etc. flags buffer
|
|
* @count: number of bytes to process
|
|
*
|
|
* Callers other than flush_to_ldisc() need to exclude the kworker from
|
|
* concurrent use of the line discipline, see paste_selection().
|
|
*
|
|
* Returns: the number of bytes processed.
|
|
*/
|
|
int tty_ldisc_receive_buf(struct tty_ldisc *ld, const unsigned char *p,
|
|
const char *f, int count)
|
|
{
|
|
if (ld->ops->receive_buf2)
|
|
count = ld->ops->receive_buf2(ld->tty, p, f, count);
|
|
else {
|
|
count = min_t(int, count, ld->tty->receive_room);
|
|
if (count && ld->ops->receive_buf)
|
|
ld->ops->receive_buf(ld->tty, p, f, count);
|
|
}
|
|
return count;
|
|
}
|
|
EXPORT_SYMBOL_GPL(tty_ldisc_receive_buf);
|
|
|
|
static int
|
|
receive_buf(struct tty_port *port, struct tty_buffer *head, int count)
|
|
{
|
|
unsigned char *p = char_buf_ptr(head, head->read);
|
|
const char *f = NULL;
|
|
int n;
|
|
|
|
if (~head->flags & TTYB_NORMAL)
|
|
f = flag_buf_ptr(head, head->read);
|
|
|
|
n = port->client_ops->receive_buf(port, p, f, count);
|
|
if (n > 0)
|
|
memset(p, 0, n);
|
|
return n;
|
|
}
|
|
|
|
/**
|
|
* flush_to_ldisc - flush data from buffer to ldisc
|
|
* @work: tty structure passed from work queue.
|
|
*
|
|
* This routine is called out of the software interrupt to flush data from the
|
|
* buffer chain to the line discipline.
|
|
*
|
|
* The receive_buf() method is single threaded for each tty instance.
|
|
*
|
|
* Locking: takes buffer lock to ensure single-threaded flip buffer 'consumer'.
|
|
*/
|
|
static void flush_to_ldisc(struct work_struct *work)
|
|
{
|
|
struct tty_port *port = container_of(work, struct tty_port, buf.work);
|
|
struct tty_bufhead *buf = &port->buf;
|
|
|
|
mutex_lock(&buf->lock);
|
|
|
|
while (1) {
|
|
struct tty_buffer *head = buf->head;
|
|
struct tty_buffer *next;
|
|
int count;
|
|
|
|
/* Ldisc or user is trying to gain exclusive access */
|
|
if (atomic_read(&buf->priority))
|
|
break;
|
|
|
|
/* paired w/ release in __tty_buffer_request_room();
|
|
* ensures commit value read is not stale if the head
|
|
* is advancing to the next buffer
|
|
*/
|
|
next = smp_load_acquire(&head->next);
|
|
/* paired w/ release in __tty_buffer_request_room() or in
|
|
* tty_buffer_flush(); ensures we see the committed buffer data
|
|
*/
|
|
count = smp_load_acquire(&head->commit) - head->read;
|
|
if (!count) {
|
|
if (next == NULL)
|
|
break;
|
|
buf->head = next;
|
|
tty_buffer_free(port, head);
|
|
continue;
|
|
}
|
|
|
|
count = receive_buf(port, head, count);
|
|
if (!count)
|
|
break;
|
|
head->read += count;
|
|
|
|
if (need_resched())
|
|
cond_resched();
|
|
}
|
|
|
|
mutex_unlock(&buf->lock);
|
|
|
|
}
|
|
|
|
/**
|
|
* tty_flip_buffer_push - push terminal buffers
|
|
* @port: tty port to push
|
|
*
|
|
* Queue a push of the terminal flip buffers to the line discipline. Can be
|
|
* called from IRQ/atomic context.
|
|
*
|
|
* In the event of the queue being busy for flipping the work will be held off
|
|
* and retried later.
|
|
*/
|
|
void tty_flip_buffer_push(struct tty_port *port)
|
|
{
|
|
struct tty_bufhead *buf = &port->buf;
|
|
|
|
/*
|
|
* Paired w/ acquire in flush_to_ldisc(); ensures flush_to_ldisc() sees
|
|
* buffer data.
|
|
*/
|
|
smp_store_release(&buf->tail->commit, buf->tail->used);
|
|
queue_work(system_unbound_wq, &buf->work);
|
|
}
|
|
EXPORT_SYMBOL(tty_flip_buffer_push);
|
|
|
|
/**
|
|
* tty_buffer_init - prepare a tty buffer structure
|
|
* @port: tty port to initialise
|
|
*
|
|
* Set up the initial state of the buffer management for a tty device. Must be
|
|
* called before the other tty buffer functions are used.
|
|
*/
|
|
void tty_buffer_init(struct tty_port *port)
|
|
{
|
|
struct tty_bufhead *buf = &port->buf;
|
|
|
|
mutex_init(&buf->lock);
|
|
tty_buffer_reset(&buf->sentinel, 0);
|
|
buf->head = &buf->sentinel;
|
|
buf->tail = &buf->sentinel;
|
|
init_llist_head(&buf->free);
|
|
atomic_set(&buf->mem_used, 0);
|
|
atomic_set(&buf->priority, 0);
|
|
INIT_WORK(&buf->work, flush_to_ldisc);
|
|
buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT;
|
|
}
|
|
|
|
/**
|
|
* tty_buffer_set_limit - change the tty buffer memory limit
|
|
* @port: tty port to change
|
|
* @limit: memory limit to set
|
|
*
|
|
* Change the tty buffer memory limit.
|
|
*
|
|
* Must be called before the other tty buffer functions are used.
|
|
*/
|
|
int tty_buffer_set_limit(struct tty_port *port, int limit)
|
|
{
|
|
if (limit < MIN_TTYB_SIZE)
|
|
return -EINVAL;
|
|
port->buf.mem_limit = limit;
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(tty_buffer_set_limit);
|
|
|
|
/* slave ptys can claim nested buffer lock when handling BRK and INTR */
|
|
void tty_buffer_set_lock_subclass(struct tty_port *port)
|
|
{
|
|
lockdep_set_subclass(&port->buf.lock, TTY_LOCK_SLAVE);
|
|
}
|
|
|
|
bool tty_buffer_restart_work(struct tty_port *port)
|
|
{
|
|
return queue_work(system_unbound_wq, &port->buf.work);
|
|
}
|
|
|
|
bool tty_buffer_cancel_work(struct tty_port *port)
|
|
{
|
|
return cancel_work_sync(&port->buf.work);
|
|
}
|
|
|
|
void tty_buffer_flush_work(struct tty_port *port)
|
|
{
|
|
flush_work(&port->buf.work);
|
|
}
|