diff options
Diffstat (limited to 'debian/patches-rt/0092-printk-remove-logbuf_lock.patch')
| -rw-r--r-- | debian/patches-rt/0092-printk-remove-logbuf_lock.patch | 486 |
1 files changed, 486 insertions, 0 deletions
diff --git a/debian/patches-rt/0092-printk-remove-logbuf_lock.patch b/debian/patches-rt/0092-printk-remove-logbuf_lock.patch new file mode 100644 index 000000000..6f45ee8b3 --- /dev/null +++ b/debian/patches-rt/0092-printk-remove-logbuf_lock.patch @@ -0,0 +1,486 @@ +From 74a8c8a0d6b64df822c5946a582ca3adeec24e63 Mon Sep 17 00:00:00 2001 +From: John Ogness <john.ogness@linutronix.de> +Date: Tue, 26 Jan 2021 17:43:19 +0106 +Subject: [PATCH 092/323] printk: remove logbuf_lock +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz + +Since the ringbuffer is lockless, there is no need for it to be +protected by @logbuf_lock. Remove @logbuf_lock. + +This means that printk_nmi_direct and printk_safe_flush_on_panic() +no longer need to acquire any lock to run. + +@console_seq, @exclusive_console_stop_seq, @console_dropped are +protected by @console_lock. + +Signed-off-by: John Ogness <john.ogness@linutronix.de> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + kernel/printk/internal.h | 4 +- + kernel/printk/printk.c | 118 ++++++++++++------------------------ + kernel/printk/printk_safe.c | 29 +++------ + 3 files changed, 48 insertions(+), 103 deletions(-) + +diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h +index 3a8fd491758c..e7acc2888c8e 100644 +--- a/kernel/printk/internal.h ++++ b/kernel/printk/internal.h +@@ -12,8 +12,6 @@ + + #define PRINTK_NMI_CONTEXT_OFFSET 0x010000000 + +-extern raw_spinlock_t logbuf_lock; +- + __printf(4, 0) + int vprintk_store(int facility, int level, + const struct dev_printk_info *dev_info, +@@ -59,7 +57,7 @@ void defer_console_output(void); + __printf(1, 0) int vprintk_func(const char *fmt, va_list args) { return 0; } + + /* +- * In !PRINTK builds we still export logbuf_lock spin_lock, console_sem ++ * In !PRINTK builds we still export console_sem + * semaphore and some of console functions (console_unlock()/etc.), so + * printk-safe must preserve the existing local IRQ guarantees. + */ +diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c +index b992be31824f..dde1696d7564 100644 +--- a/kernel/printk/printk.c ++++ b/kernel/printk/printk.c +@@ -357,41 +357,6 @@ enum log_flags { + LOG_CONT = 8, /* text is a fragment of a continuation line */ + }; + +-/* +- * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken +- * within the scheduler's rq lock. It must be released before calling +- * console_unlock() or anything else that might wake up a process. +- */ +-DEFINE_RAW_SPINLOCK(logbuf_lock); +- +-/* +- * Helper macros to lock/unlock logbuf_lock and switch between +- * printk-safe/unsafe modes. +- */ +-#define logbuf_lock_irq() \ +- do { \ +- printk_safe_enter_irq(); \ +- raw_spin_lock(&logbuf_lock); \ +- } while (0) +- +-#define logbuf_unlock_irq() \ +- do { \ +- raw_spin_unlock(&logbuf_lock); \ +- printk_safe_exit_irq(); \ +- } while (0) +- +-#define logbuf_lock_irqsave(flags) \ +- do { \ +- printk_safe_enter_irqsave(flags); \ +- raw_spin_lock(&logbuf_lock); \ +- } while (0) +- +-#define logbuf_unlock_irqrestore(flags) \ +- do { \ +- raw_spin_unlock(&logbuf_lock); \ +- printk_safe_exit_irqrestore(flags); \ +- } while (0) +- + /* syslog_lock protects syslog_* variables and write access to clear_seq. */ + static DEFINE_RAW_SPINLOCK(syslog_lock); + +@@ -403,6 +368,7 @@ static u64 syslog_seq; + static size_t syslog_partial; + static bool syslog_time; + ++/* All 3 protected by @console_sem. */ + /* the next printk record to write to the console */ + static u64 console_seq; + static u64 exclusive_console_stop_seq; +@@ -769,27 +735,27 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, + if (ret) + return ret; + +- logbuf_lock_irq(); ++ printk_safe_enter_irq(); + if (!prb_read_valid(prb, atomic64_read(&user->seq), r)) { + if (file->f_flags & O_NONBLOCK) { + ret = -EAGAIN; +- logbuf_unlock_irq(); ++ printk_safe_exit_irq(); + goto out; + } + +- logbuf_unlock_irq(); ++ printk_safe_exit_irq(); + ret = wait_event_interruptible(log_wait, + prb_read_valid(prb, atomic64_read(&user->seq), r)); + if (ret) + goto out; +- logbuf_lock_irq(); ++ printk_safe_enter_irq(); + } + + if (r->info->seq != atomic64_read(&user->seq)) { + /* our last seen message is gone, return error and reset */ + atomic64_set(&user->seq, r->info->seq); + ret = -EPIPE; +- logbuf_unlock_irq(); ++ printk_safe_exit_irq(); + goto out; + } + +@@ -799,7 +765,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, + &r->info->dev_info); + + atomic64_set(&user->seq, r->info->seq + 1); +- logbuf_unlock_irq(); ++ printk_safe_exit_irq(); + + if (len > count) { + ret = -EINVAL; +@@ -834,7 +800,7 @@ static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence) + if (offset) + return -ESPIPE; + +- logbuf_lock_irq(); ++ printk_safe_enter_irq(); + switch (whence) { + case SEEK_SET: + /* the first record */ +@@ -855,7 +821,7 @@ static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence) + default: + ret = -EINVAL; + } +- logbuf_unlock_irq(); ++ printk_safe_exit_irq(); + return ret; + } + +@@ -870,15 +836,15 @@ static __poll_t devkmsg_poll(struct file *file, poll_table *wait) + + poll_wait(file, &log_wait, wait); + +- logbuf_lock_irq(); +- if (prb_read_valid_info(prb, user->seq, &info, NULL)) { ++ printk_safe_enter_irq(); ++ if (prb_read_valid_info(prb, atomic64_read(&user->seq), &info, NULL)) { + /* return error when data has vanished underneath us */ + if (info.seq != atomic64_read(&user->seq)) + ret = EPOLLIN|EPOLLRDNORM|EPOLLERR|EPOLLPRI; + else + ret = EPOLLIN|EPOLLRDNORM; + } +- logbuf_unlock_irq(); ++ printk_safe_exit_irq(); + + return ret; + } +@@ -911,9 +877,9 @@ static int devkmsg_open(struct inode *inode, struct file *file) + prb_rec_init_rd(&user->record, &user->info, + &user->text_buf[0], sizeof(user->text_buf)); + +- logbuf_lock_irq(); ++ printk_safe_enter_irq(); + atomic64_set(&user->seq, prb_first_valid_seq(prb)); +- logbuf_unlock_irq(); ++ printk_safe_exit_irq(); + + file->private_data = user; + return 0; +@@ -1535,11 +1501,11 @@ static int syslog_print(char __user *buf, int size) + size_t n; + size_t skip; + +- logbuf_lock_irq(); ++ printk_safe_enter_irq(); + raw_spin_lock(&syslog_lock); + if (!prb_read_valid(prb, syslog_seq, &r)) { + raw_spin_unlock(&syslog_lock); +- logbuf_unlock_irq(); ++ printk_safe_exit_irq(); + break; + } + if (r.info->seq != syslog_seq) { +@@ -1569,7 +1535,7 @@ static int syslog_print(char __user *buf, int size) + } else + n = 0; + raw_spin_unlock(&syslog_lock); +- logbuf_unlock_irq(); ++ printk_safe_exit_irq(); + + if (!n) + break; +@@ -1603,7 +1569,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) + return -ENOMEM; + + time = printk_time; +- logbuf_lock_irq(); ++ printk_safe_enter_irq(); + /* + * Find first record that fits, including all following records, + * into the user-provided buffer for this dump. +@@ -1624,12 +1590,12 @@ static int syslog_print_all(char __user *buf, int size, bool clear) + break; + } + +- logbuf_unlock_irq(); ++ printk_safe_exit_irq(); + if (copy_to_user(buf + len, text, textlen)) + len = -EFAULT; + else + len += textlen; +- logbuf_lock_irq(); ++ printk_safe_enter_irq(); + + if (len < 0) + break; +@@ -1640,7 +1606,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) + latched_seq_write(&clear_seq, seq); + raw_spin_unlock(&syslog_lock); + } +- logbuf_unlock_irq(); ++ printk_safe_exit_irq(); + + kfree(text); + return len; +@@ -1648,11 +1614,11 @@ static int syslog_print_all(char __user *buf, int size, bool clear) + + static void syslog_clear(void) + { +- logbuf_lock_irq(); ++ printk_safe_enter_irq(); + raw_spin_lock(&syslog_lock); + latched_seq_write(&clear_seq, prb_next_seq(prb)); + raw_spin_unlock(&syslog_lock); +- logbuf_unlock_irq(); ++ printk_safe_exit_irq(); + } + + /* Return a consistent copy of @syslog_seq. */ +@@ -1740,12 +1706,12 @@ int do_syslog(int type, char __user *buf, int len, int source) + break; + /* Number of chars in the log buffer */ + case SYSLOG_ACTION_SIZE_UNREAD: +- logbuf_lock_irq(); ++ printk_safe_enter_irq(); + raw_spin_lock(&syslog_lock); + if (!prb_read_valid_info(prb, syslog_seq, &info, NULL)) { + /* No unread messages. */ + raw_spin_unlock(&syslog_lock); +- logbuf_unlock_irq(); ++ printk_safe_exit_irq(); + return 0; + } + if (info.seq != syslog_seq) { +@@ -1774,7 +1740,7 @@ int do_syslog(int type, char __user *buf, int len, int source) + error -= syslog_partial; + } + raw_spin_unlock(&syslog_lock); +- logbuf_unlock_irq(); ++ printk_safe_exit_irq(); + break; + /* Size of the log buffer */ + case SYSLOG_ACTION_SIZE_BUFFER: +@@ -2630,7 +2596,6 @@ void console_unlock(void) + size_t len; + + printk_safe_enter_irqsave(flags); +- raw_spin_lock(&logbuf_lock); + skip: + if (!prb_read_valid(prb, console_seq, &r)) + break; +@@ -2674,7 +2639,6 @@ void console_unlock(void) + console_msg_format & MSG_FORMAT_SYSLOG, + printk_time); + console_seq++; +- raw_spin_unlock(&logbuf_lock); + + /* + * While actively printing out messages, if another printk() +@@ -2701,8 +2665,6 @@ void console_unlock(void) + + console_locked = 0; + +- raw_spin_unlock(&logbuf_lock); +- + up_console_sem(); + + /* +@@ -2711,9 +2673,7 @@ void console_unlock(void) + * there's a new owner and the console_unlock() from them will do the + * flush, no worries. + */ +- raw_spin_lock(&logbuf_lock); + retry = prb_read_valid(prb, console_seq, NULL); +- raw_spin_unlock(&logbuf_lock); + printk_safe_exit_irqrestore(flags); + + if (retry && console_trylock()) +@@ -2780,9 +2740,9 @@ void console_flush_on_panic(enum con_flush_mode mode) + if (mode == CONSOLE_REPLAY_ALL) { + unsigned long flags; + +- logbuf_lock_irqsave(flags); ++ printk_safe_enter_irqsave(flags); + console_seq = prb_first_valid_seq(prb); +- logbuf_unlock_irqrestore(flags); ++ printk_safe_exit_irqrestore(flags); + } + console_unlock(); + } +@@ -3011,7 +2971,7 @@ void register_console(struct console *newcon) + * console_unlock(); will print out the buffered messages + * for us. + */ +- logbuf_lock_irqsave(flags); ++ printk_safe_enter_irqsave(flags); + /* + * We're about to replay the log buffer. Only do this to the + * just-registered console to avoid excessive message spam to +@@ -3029,7 +2989,7 @@ void register_console(struct console *newcon) + console_seq = syslog_seq; + raw_spin_unlock(&syslog_lock); + +- logbuf_unlock_irqrestore(flags); ++ printk_safe_exit_irqrestore(flags); + } + console_unlock(); + console_sysfs_notify(); +@@ -3415,10 +3375,10 @@ void kmsg_dump(enum kmsg_dump_reason reason) + + /* initialize iterator with data about the stored records */ + iter.active = true; +- logbuf_lock_irqsave(flags); ++ printk_safe_enter_irqsave(flags); + iter.cur_seq = latched_seq_read_nolock(&clear_seq); + iter.next_seq = prb_next_seq(prb); +- logbuf_unlock_irqrestore(flags); ++ printk_safe_exit_irqrestore(flags); + + /* invoke dumper which will iterate over records */ + dumper->dump(dumper, reason, &iter); +@@ -3505,9 +3465,9 @@ bool kmsg_dump_get_line(struct kmsg_dumper_iter *iter, bool syslog, + unsigned long flags; + bool ret; + +- logbuf_lock_irqsave(flags); ++ printk_safe_enter_irqsave(flags); + ret = kmsg_dump_get_line_nolock(iter, syslog, line, size, len); +- logbuf_unlock_irqrestore(flags); ++ printk_safe_exit_irqrestore(flags); + + return ret; + } +@@ -3547,7 +3507,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper_iter *iter, bool syslog, + if (!iter->active || !buf || !size) + goto out; + +- logbuf_lock_irqsave(flags); ++ printk_safe_enter_irqsave(flags); + if (prb_read_valid_info(prb, iter->cur_seq, &info, NULL)) { + if (info.seq != iter->cur_seq) { + /* messages are gone, move to first available one */ +@@ -3557,7 +3517,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper_iter *iter, bool syslog, + + /* last entry */ + if (iter->cur_seq >= iter->next_seq) { +- logbuf_unlock_irqrestore(flags); ++ printk_safe_exit_irqrestore(flags); + goto out; + } + +@@ -3591,7 +3551,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper_iter *iter, bool syslog, + + iter->next_seq = next_seq; + ret = true; +- logbuf_unlock_irqrestore(flags); ++ printk_safe_exit_irqrestore(flags); + out: + if (len_out) + *len_out = len; +@@ -3627,9 +3587,9 @@ void kmsg_dump_rewind(struct kmsg_dumper_iter *iter) + { + unsigned long flags; + +- logbuf_lock_irqsave(flags); ++ printk_safe_enter_irqsave(flags); + kmsg_dump_rewind_nolock(iter); +- logbuf_unlock_irqrestore(flags); ++ printk_safe_exit_irqrestore(flags); + } + EXPORT_SYMBOL_GPL(kmsg_dump_rewind); + +diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c +index 2e9e3ed7d63e..7df8a88d4115 100644 +--- a/kernel/printk/printk_safe.c ++++ b/kernel/printk/printk_safe.c +@@ -16,7 +16,7 @@ + #include "internal.h" + + /* +- * printk() could not take logbuf_lock in NMI context. Instead, ++ * In NMI and safe mode, printk() avoids taking locks. Instead, + * it uses an alternative implementation that temporary stores + * the strings into a per-CPU buffer. The content of the buffer + * is later flushed into the main ring buffer via IRQ work. +@@ -266,18 +266,6 @@ void printk_safe_flush(void) + */ + void printk_safe_flush_on_panic(void) + { +- /* +- * Make sure that we could access the main ring buffer. +- * Do not risk a double release when more CPUs are up. +- */ +- if (raw_spin_is_locked(&logbuf_lock)) { +- if (num_online_cpus() > 1) +- return; +- +- debug_locks_off(); +- raw_spin_lock_init(&logbuf_lock); +- } +- + if (raw_spin_is_locked(&safe_read_lock)) { + if (num_online_cpus() > 1) + return; +@@ -319,9 +307,7 @@ void noinstr printk_nmi_exit(void) + * reordering. + * + * It has effect only when called in NMI context. Then printk() +- * will try to store the messages into the main logbuf directly +- * and use the per-CPU buffers only as a fallback when the lock +- * is not available. ++ * will store the messages into the main logbuf directly. + */ + void printk_nmi_direct_enter(void) + { +@@ -376,20 +362,21 @@ __printf(1, 0) int vprintk_func(const char *fmt, va_list args) + #endif + + /* +- * Try to use the main logbuf even in NMI. But avoid calling console ++ * Use the main logbuf even in NMI. But avoid calling console + * drivers that might have their own locks. + */ +- if ((this_cpu_read(printk_context) & PRINTK_NMI_DIRECT_CONTEXT_MASK) && +- raw_spin_trylock(&logbuf_lock)) { ++ if ((this_cpu_read(printk_context) & PRINTK_NMI_DIRECT_CONTEXT_MASK)) { ++ unsigned long flags; + int len; + ++ printk_safe_enter_irqsave(flags); + len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, fmt, args); +- raw_spin_unlock(&logbuf_lock); ++ printk_safe_exit_irqrestore(flags); + defer_console_output(); + return len; + } + +- /* Use extra buffer in NMI when logbuf_lock is taken or in safe mode. */ ++ /* Use extra buffer in NMI. */ + if (this_cpu_read(printk_context) & PRINTK_NMI_CONTEXT_MASK) + return vprintk_nmi(fmt, args); + +-- +2.43.0 + |