/* * linux/kernel/printk.c * * Copyright (C) 1991, 1992 Linus Torvalds * * Modified to make sys_syslog() more flexible: added commands to * return the last 4k of kernel messages, regardless of whether * they've been read or not. Added option to suppress kernel printk's * to the console. Added hook for sending the console messages * elsewhere, in preparation for a serial line console (someday). * Ted Ts'o, 2/11/93. * Modified for sysctl support, 1/8/97, Chris Horn. * Fixed SMP synchronization, 08/08/99, Manfred Spraul * manfreds@colorfullife.com * Rewrote bits to get rid of console_lock * 01Mar01 Andrew Morton <andrewm@uow.edu.au> */ #include <linux/kernel.h>#include <linux/mm.h>#include <linux/tty.h>#include <linux/tty_driver.h>#include <linux/smp_lock.h>#include <linux/console.h>#include <linux/init.h>#include <linux/module.h>#include <linux/interrupt.h> /* For in_interrupt() */#include <linux/config.h>#include <linux/delay.h>#include <linux/smp.h>#include <linux/security.h>#include <linux/bootmem.h>#include <linux/syscalls.h> #include <asm/uaccess.h> #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT) /* printk's without a loglevel use this.. */#define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */ /* We show everything that is MORE important than this.. */#define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */#define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */ DECLARE_WAIT_QUEUE_HEAD(log_wait); int console_printk[4] = { DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */ DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */ MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */ DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */}; EXPORT_SYMBOL(console_printk); /* * Low lever drivers may need that to know if they can schedule in * their unblank() callback or not. So let's export it. */int oops_in_progress;EXPORT_SYMBOL(oops_in_progress); /* * console_sem protects the console_drivers list, and also * provides serialisation for access to the entire console * driver system. */static DECLARE_MUTEX(console_sem);struct console *console_drivers;/* * This is used for debugging the mess that is the VT code by * keeping track if we have the console semaphore held. It's * definitely not the perfect debug tool (we don't know if _WE_ * hold it are racing, but it helps tracking those weird code * path in the console code where we end up in places I want * locked without the console sempahore held */static int console_locked; /* * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars * It is also used in interesting ways to provide interlocking in * release_console_sem(). */static DEFINE_SPINLOCK(logbuf_lock); #define LOG_BUF_MASK (log_buf_len-1)#define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK]) /* * The indices into log_buf are not constrained to log_buf_len - they * must be masked before subscripting */static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */static unsigned long log_end; /* Index into log_buf: most-recently-written-char + 1 */ /* * Array of consoles built from command line options (console=) */struct console_cmdline{ char name[8]; /* Name of the driver */ int index; /* Minor dev. to use */ char *options; /* Options for the driver */}; #define MAX_CMDLINECONSOLES 8 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];static int selected_console = -1;static int preferred_console = -1; /* Flag: console code may call schedule() */static int console_may_schedule; #ifdef CONFIG_PRINTK static char __log_buf[__LOG_BUF_LEN];static char *log_buf = __log_buf;static int log_buf_len = __LOG_BUF_LEN;static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */ /* * Setup a list of consoles. Called from init/main.c */static int __init console_setup(char *str){ char name[sizeof(console_cmdline[0].name)]; char *s, *options; int idx; /* * Decode str into name, index, options. */ if (str[0] >= '0' && str[0] <= '9') { strcpy(name, "ttyS"); strncpy(name + 4, str, sizeof(name) - 5); } else strncpy(name, str, sizeof(name) - 1); name[sizeof(name) - 1] = 0; if ((options = strchr(str, ',')) != NULL) *(options++) = 0;#ifdef __sparc__ if (!strcmp(str, "ttya")) strcpy(name, "ttyS0"); if (!strcmp(str, "ttyb")) strcpy(name, "ttyS1");#endif for(s = name; *s; s++) if ((*s >= '0' && *s <= '9') || *s == ',') break; idx = simple_strtoul(s, NULL, 10); *s = 0; add_preferred_console(name, idx, options); return 1;} __setup("console=", console_setup); static int __init log_buf_len_setup(char *str){ unsigned long size = memparse(str, &str); unsigned long flags; if (size) size = roundup_pow_of_two(size); if (size > log_buf_len) { unsigned long start, dest_idx, offset; char * new_log_buf; new_log_buf = alloc_bootmem(size); if (!new_log_buf) { printk("log_buf_len: allocation failed\n"); goto out; } spin_lock_irqsave(&logbuf_lock, flags); log_buf_len = size; log_buf = new_log_buf; offset = start = min(con_start, log_start); dest_idx = 0; while (start != log_end) { log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)]; start++; dest_idx++; } log_start -= offset; con_start -= offset; log_end -= offset; spin_unlock_irqrestore(&logbuf_lock, flags); printk("log_buf_len: %d\n", log_buf_len); }out: return 1;} __setup("log_buf_len=", log_buf_len_setup); /* * Commands to do_syslog: * * 0 -- Close the log. Currently a NOP. * 1 -- Open the log. Currently a NOP. * 2 -- Read from the log. * 3 -- Read all messages remaining in the ring buffer. * 4 -- Read and clear all messages remaining in the ring buffer * 5 -- Clear ring buffer. * 6 -- Disable printk's to console * 7 -- Enable printk's to console * 8 -- Set level of messages printed to console * 9 -- Return number of unread characters in the log buffer * 10 -- Return size of the log buffer */int do_syslog(int type, char __user * buf, int len){ unsigned long i, j, limit, count; int do_clear = 0; char c; int error = 0; error = security_syslog(type); if (error) return error; switch (type) { case 0: /* Close log */ break; case 1: /* Open log */ break; case 2: /* Read from log */ error = -EINVAL; if (!buf || len < 0) goto out; error = 0; if (!len) goto out; if (!access_ok(VERIFY_WRITE, buf, len)) { error = -EFAULT; goto out; } error = wait_event_interruptible(log_wait, (log_start - log_end)); if (error) goto out; i = 0; spin_lock_irq(&logbuf_lock); while (!error && (log_start != log_end) && i < len) { c = LOG_BUF(log_start); log_start++; spin_unlock_irq(&logbuf_lock); error = __put_user(c,buf); buf++; i++; cond_resched(); spin_lock_irq(&logbuf_lock); } spin_unlock_irq(&logbuf_lock); if (!error) error = i; break; case 4: /* Read/clear last kernel messages */ do_clear = 1; /* FALL THRU */ case 3: /* Read last kernel messages */ error = -EINVAL; if (!buf || len < 0) goto out; error = 0; if (!len) goto out; if (!access_ok(VERIFY_WRITE, buf, len)) { error = -EFAULT; goto out; } count = len; if (count > log_buf_len) count = log_buf_len; spin_lock_irq(&logbuf_lock); if (count > logged_chars) count = logged_chars; if (do_clear) logged_chars = 0; limit = log_end; /* * __put_user() could sleep, and while we sleep * printk() could overwrite the messages * we try to copy to user space. Therefore * the messages are copied in reverse. <manfreds> */ for(i = 0; i < count && !error; i++) { j = limit-1-i; if (j + log_buf_len < log_end) break; c = LOG_BUF(j); spin_unlock_irq(&logbuf_lock); error = __put_user(c,&buf[count-1-i]); cond_resched(); spin_lock_irq(&logbuf_lock); } spin_unlock_irq(&logbuf_lock); if (error) break; error = i; if(i != count) { int offset = count-error; /* buffer overflow during copy, correct user buffer. */ for(i=0;i<error;i++) { if (__get_user(c,&buf[i+offset]) || __put_user(c,&buf[i])) { error = -EFAULT; break; } cond_resched(); } } break; case 5: /* Clear ring buffer */ logged_chars = 0; break; case 6: /* Disable logging to console */ console_loglevel = minimum_console_loglevel; break; case 7: /* Enable logging to console */ console_loglevel = default_console_loglevel; break; case 8: /* Set level of messages printed to console */ error = -EINVAL; if (len < 1 || len > 8) goto out; if (len < minimum_console_loglevel) len = minimum_console_loglevel; console_loglevel = len; error = 0; break; case 9: /* Number of chars in the log buffer */ error = log_end - log_start; break; case 10: /* Size of the log buffer */ error = log_buf_len; break; default: error = -EINVAL; break; }out: return error;} asmlinkage long sys_syslog(int type, char __user * buf, int len){ return do_syslog(type, buf, len);} /* * Call the console drivers on a range of log_buf */static void __call_console_drivers(unsigned long start, unsigned long end){ struct console *con; for (con = console_drivers; con; con = con->next) { if ((con->flags & CON_ENABLED) && con->write) con->write(con, &LOG_BUF(start), end - start); }} /* * Write out chars from start to end - 1 inclusive */static void _call_console_drivers(unsigned long start, unsigned long end, int msg_log_level){ if (msg_log_level < console_loglevel && console_drivers && start != end) { if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) { /* wrapped write */ __call_console_drivers(start & LOG_BUF_MASK, log_buf_len); __call_console_drivers(0, end & LOG_BUF_MASK); } else { __call_console_drivers(start, end); } }} /* * Call the console drivers, asking them to write out * log_buf[start] to log_buf[end - 1]. * The console_sem must be held. */static void call_console_drivers(unsigned long start, unsigned long end){ unsigned long cur_index, start_print; static int msg_level = -1; if (((long)(start - end)) > 0) BUG(); cur_index = start; start_print = start; while (cur_index != end) { if ( msg_level < 0 && ((end - cur_index) > 2) && LOG_BUF(cur_index + 0) == '<' && LOG_BUF(cur_index + 1) >= '0' && LOG_BUF(cur_index + 1) <= '7' && LOG_BUF(cur_index + 2) == '>') { msg_level = LOG_BUF(cur_index + 1) - '0'; cur_index += 3; start_print = cur_index; } while (cur_index != end) { char c = LOG_BUF(cur_index); cur_index++; if (c == '\n') { if (msg_level < 0) { /* * printk() has already given us loglevel tags in * the buffer. This code is here in case the * log buffer has wrapped right round and scribbled * on those tags */ msg_level = default_message_loglevel; } _call_console_drivers(start_print, cur_index, msg_level); msg_level = -1; start_print = cur_index; break; } } } _call_console_drivers(start_print, end, msg_level);} static void emit_log_char(char c){ LOG_BUF(log_end) = c; log_end++; if (log_end - log_start > log_buf_len) log_start = log_end - log_buf_len; if (log_end - con_start > log_buf_len) con_start = log_end - log_buf_len; if (logged_chars < log_buf_len) logged_chars++;} /* * Zap console related locks when oopsing. Only zap at most once * every 10 seconds, to leave time for slow consoles to print a * full oops. */static void zap_locks(void){ static unsigned long oops_timestamp; if (time_after_eq(jiffies, oops_timestamp) && !time_after(jiffies, oops_timestamp + 30*HZ)) return; oops_timestamp = jiffies; /* If a crash is occurring, make sure we can't deadlock */ spin_lock_init(&logbuf_lock); /* And make sure that we print immediately */ init_MUTEX(&console_sem);} #if defined(CONFIG_PRINTK_TIME)static int printk_time = 1;#elsestatic int printk_time = 0;#endif static int __init printk_time_setup(char *str){ if (*str) return 0; printk_time = 1; return 1;} __setup("time", printk_time_setup); /* * This is printk. It can be called from any context. We want it to work. * * We try to grab the console_sem. If we succeed, it's easy - we log the output and * call the console drivers. If we fail to get the semaphore we place the output * into the log buffer and return. The current holder of the console_sem will * notice the new output in release_console_sem() and will send it to the * consoles before releasing the semaphore. * * One effect of this deferred printing is that code which calls printk() andLines 1–500 of 1018. Load more
/* * linux/kernel/printk.c * * Copyright (C) 1991, 1992 Linus Torvalds * * Modified to make sys_syslog() more flexible: added commands to * return the last 4k of kernel messages, regardless of whether * they've been read or not. Added option to suppress kernel printk's * to the console. Added hook for sending the console messages * elsewhere, in preparation for a serial line console (someday). * Ted Ts'o, 2/11/93. * Modified for sysctl support, 1/8/97, Chris Horn. * Fixed SMP synchronization, 08/08/99, Manfred Spraul * manfreds@colorfullife.com * Rewrote bits to get rid of console_lock * 01Mar01 Andrew Morton <andrewm@uow.edu.au> */ #include <linux/kernel.h> #include <linux/mm.h> #include <linux/tty.h> #include <linux/tty_driver.h> #include <linux/smp_lock.h> #include <linux/console.h> #include <linux/init.h> #include <linux/module.h> #include <linux/interrupt.h> /* For in_interrupt() */ #include <linux/config.h> #include <linux/delay.h> #include <linux/smp.h> #include <linux/security.h> #include <linux/bootmem.h> #include <linux/syscalls.h> #include <asm/uaccess.h> #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT) /* printk's without a loglevel use this.. */ #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */ /* We show everything that is MORE important than this.. */ #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */ #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */ DECLARE_WAIT_QUEUE_HEAD(log_wait); int console_printk[4] = { DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */ DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */ MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */ DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */ }; EXPORT_SYMBOL(console_printk); /* * Low lever drivers may need that to know if they can schedule in * their unblank() callback or not. So let's export it. */ int oops_in_progress; EXPORT_SYMBOL(oops_in_progress); /* * console_sem protects the console_drivers list, and also * provides serialisation for access to the entire console * driver system. */ static DECLARE_MUTEX(console_sem); struct console *console_drivers; /* * This is used for debugging the mess that is the VT code by * keeping track if we have the console semaphore held. It's * definitely not the perfect debug tool (we don't know if _WE_ * hold it are racing, but it helps tracking those weird code * path in the console code where we end up in places I want * locked without the console sempahore held */ static int console_locked; /* * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars * It is also used in interesting ways to provide interlocking in * release_console_sem(). */ static DEFINE_SPINLOCK(logbuf_lock); #define LOG_BUF_MASK (log_buf_len-1) #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK]) /* * The indices into log_buf are not constrained to log_buf_len - they * must be masked before subscripting */ static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */ static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */ static unsigned long log_end; /* Index into log_buf: most-recently-written-char + 1 */ /* * Array of consoles built from command line options (console=) */ struct console_cmdline { char name[8]; /* Name of the driver */ int index; /* Minor dev. to use */ char *options; /* Options for the driver */ }; #define MAX_CMDLINECONSOLES 8 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES]; static int selected_console = -1; static int preferred_console = -1; /* Flag: console code may call schedule() */ static int console_may_schedule; #ifdef CONFIG_PRINTK static char __log_buf[__LOG_BUF_LEN]; static char *log_buf = __log_buf; static int log_buf_len = __LOG_BUF_LEN; static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */ /* * Setup a list of consoles. Called from init/main.c */ static int __init console_setup(char *str) { char name[sizeof(console_cmdline[0].name)]; char *s, *options; int idx; /* * Decode str into name, index, options. */ if (str[0] >= '0' && str[0] <= '9') { strcpy(name, "ttyS"); strncpy(name + 4, str, sizeof(name) - 5); } else strncpy(name, str, sizeof(name) - 1); name[sizeof(name) - 1] = 0; if ((options = strchr(str, ',')) != NULL) *(options++) = 0; #ifdef __sparc__ if (!strcmp(str, "ttya")) strcpy(name, "ttyS0"); if (!strcmp(str, "ttyb")) strcpy(name, "ttyS1"); #endif for(s = name; *s; s++) if ((*s >= '0' && *s <= '9') || *s == ',') break; idx = simple_strtoul(s, NULL, 10); *s = 0; add_preferred_console(name, idx, options); return 1; } __setup("console=", console_setup); static int __init log_buf_len_setup(char *str) { unsigned long size = memparse(str, &str); unsigned long flags; if (size) size = roundup_pow_of_two(size); if (size > log_buf_len) { unsigned long start, dest_idx, offset; char * new_log_buf; new_log_buf = alloc_bootmem(size); if (!new_log_buf) { printk("log_buf_len: allocation failed\n"); goto out; } spin_lock_irqsave(&logbuf_lock, flags); log_buf_len = size; log_buf = new_log_buf; offset = start = min(con_start, log_start); dest_idx = 0; while (start != log_end) { log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)]; start++; dest_idx++; } log_start -= offset; con_start -= offset; log_end -= offset; spin_unlock_irqrestore(&logbuf_lock, flags); printk("log_buf_len: %d\n", log_buf_len); } out: return 1; } __setup("log_buf_len=", log_buf_len_setup); /* * Commands to do_syslog: * * 0 -- Close the log. Currently a NOP. * 1 -- Open the log. Currently a NOP. * 2 -- Read from the log. * 3 -- Read all messages remaining in the ring buffer. * 4 -- Read and clear all messages remaining in the ring buffer * 5 -- Clear ring buffer. * 6 -- Disable printk's to console * 7 -- Enable printk's to console * 8 -- Set level of messages printed to console * 9 -- Return number of unread characters in the log buffer * 10 -- Return size of the log buffer */ int do_syslog(int type, char __user * buf, int len) { unsigned long i, j, limit, count; int do_clear = 0; char c; int error = 0; error = security_syslog(type); if (error) return error; switch (type) { case 0: /* Close log */ break; case 1: /* Open log */ break; case 2: /* Read from log */ error = -EINVAL; if (!buf || len < 0) goto out; error = 0; if (!len) goto out; if (!access_ok(VERIFY_WRITE, buf, len)) { error = -EFAULT; goto out; } error = wait_event_interruptible(log_wait, (log_start - log_end)); if (error) goto out; i = 0; spin_lock_irq(&logbuf_lock); while (!error && (log_start != log_end) && i < len) { c = LOG_BUF(log_start); log_start++; spin_unlock_irq(&logbuf_lock); error = __put_user(c,buf); buf++; i++; cond_resched(); spin_lock_irq(&logbuf_lock); } spin_unlock_irq(&logbuf_lock); if (!error) error = i; break; case 4: /* Read/clear last kernel messages */ do_clear = 1; /* FALL THRU */ case 3: /* Read last kernel messages */ error = -EINVAL; if (!buf || len < 0) goto out; error = 0; if (!len) goto out; if (!access_ok(VERIFY_WRITE, buf, len)) { error = -EFAULT; goto out; } count = len; if (count > log_buf_len) count = log_buf_len; spin_lock_irq(&logbuf_lock); if (count > logged_chars) count = logged_chars; if (do_clear) logged_chars = 0; limit = log_end; /* * __put_user() could sleep, and while we sleep * printk() could overwrite the messages * we try to copy to user space. Therefore * the messages are copied in reverse. <manfreds> */ for(i = 0; i < count && !error; i++) { j = limit-1-i; if (j + log_buf_len < log_end) break; c = LOG_BUF(j); spin_unlock_irq(&logbuf_lock); error = __put_user(c,&buf[count-1-i]); cond_resched(); spin_lock_irq(&logbuf_lock); } spin_unlock_irq(&logbuf_lock); if (error) break; error = i; if(i != count) { int offset = count-error; /* buffer overflow during copy, correct user buffer. */ for(i=0;i<error;i++) { if (__get_user(c,&buf[i+offset]) || __put_user(c,&buf[i])) { error = -EFAULT; break; } cond_resched(); } } break; case 5: /* Clear ring buffer */ logged_chars = 0; break; case 6: /* Disable logging to console */ console_loglevel = minimum_console_loglevel; break; case 7: /* Enable logging to console */ console_loglevel = default_console_loglevel; break; case 8: /* Set level of messages printed to console */ error = -EINVAL; if (len < 1 || len > 8) goto out; if (len < minimum_console_loglevel) len = minimum_console_loglevel; console_loglevel = len; error = 0; break; case 9: /* Number of chars in the log buffer */ error = log_end - log_start; break; case 10: /* Size of the log buffer */ error = log_buf_len; break; default: error = -EINVAL; break; } out: return error; } asmlinkage long sys_syslog(int type, char __user * buf, int len) { return do_syslog(type, buf, len); } /* * Call the console drivers on a range of log_buf */ static void __call_console_drivers(unsigned long start, unsigned long end) { struct console *con; for (con = console_drivers; con; con = con->next) { if ((con->flags & CON_ENABLED) && con->write) con->write(con, &LOG_BUF(start), end - start); } } /* * Write out chars from start to end - 1 inclusive */ static void _call_console_drivers(unsigned long start, unsigned long end, int msg_log_level) { if (msg_log_level < console_loglevel && console_drivers && start != end) { if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) { /* wrapped write */ __call_console_drivers(start & LOG_BUF_MASK, log_buf_len); __call_console_drivers(0, end & LOG_BUF_MASK); } else { __call_console_drivers(start, end); } } } /* * Call the console drivers, asking them to write out * log_buf[start] to log_buf[end - 1]. * The console_sem must be held. */ static void call_console_drivers(unsigned long start, unsigned long end) { unsigned long cur_index, start_print; static int msg_level = -1; if (((long)(start - end)) > 0) BUG(); cur_index = start; start_print = start; while (cur_index != end) { if ( msg_level < 0 && ((end - cur_index) > 2) && LOG_BUF(cur_index + 0) == '<' && LOG_BUF(cur_index + 1) >= '0' && LOG_BUF(cur_index + 1) <= '7' && LOG_BUF(cur_index + 2) == '>') { msg_level = LOG_BUF(cur_index + 1) - '0'; cur_index += 3; start_print = cur_index; } while (cur_index != end) { char c = LOG_BUF(cur_index); cur_index++; if (c == '\n') { if (msg_level < 0) { /* * printk() has already given us loglevel tags in * the buffer. This code is here in case the * log buffer has wrapped right round and scribbled * on those tags */ msg_level = default_message_loglevel; } _call_console_drivers(start_print, cur_index, msg_level); msg_level = -1; start_print = cur_index; break; } } } _call_console_drivers(start_print, end, msg_level); } static void emit_log_char(char c) { LOG_BUF(log_end) = c; log_end++; if (log_end - log_start > log_buf_len) log_start = log_end - log_buf_len; if (log_end - con_start > log_buf_len) con_start = log_end - log_buf_len; if (logged_chars < log_buf_len) logged_chars++; } /* * Zap console related locks when oopsing. Only zap at most once * every 10 seconds, to leave time for slow consoles to print a * full oops. */ static void zap_locks(void) { static unsigned long oops_timestamp; if (time_after_eq(jiffies, oops_timestamp) && !time_after(jiffies, oops_timestamp + 30*HZ)) return; oops_timestamp = jiffies; /* If a crash is occurring, make sure we can't deadlock */ spin_lock_init(&logbuf_lock); /* And make sure that we print immediately */ init_MUTEX(&console_sem); } #if defined(CONFIG_PRINTK_TIME) static int printk_time = 1; #else static int printk_time = 0; #endif static int __init printk_time_setup(char *str) { if (*str) return 0; printk_time = 1; return 1; } __setup("time", printk_time_setup); /* * This is printk. It can be called from any context. We want it to work. * * We try to grab the console_sem. If we succeed, it's easy - we log the output and * call the console drivers. If we fail to get the semaphore we place the output * into the log buffer and return. The current holder of the console_sem will * notice the new output in release_console_sem() and will send it to the * consoles before releasing the semaphore. * * One effect of this deferred printing is that code which calls printk() and