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Diffstat (limited to 'Documentation/trace/ftrace.rst')
| -rw-r--r-- | Documentation/trace/ftrace.rst | 372 |
1 files changed, 322 insertions, 50 deletions
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index d2b5657ed33e..7e7b8ec17934 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -34,13 +34,13 @@ Throughout the kernel is hundreds of static event points that can be enabled via the tracefs file system to see what is going on in certain parts of the kernel. -See events.txt for more information. +See events.rst for more information. Implementation Details ---------------------- -See :doc:`ftrace-design` for details for arch porters and such. +See Documentation/trace/ftrace-design.rst for details for arch porters and such. The File System @@ -95,7 +95,8 @@ of ftrace. Here is a list of some of the key files: current_tracer: This is used to set or display the current tracer - that is configured. + that is configured. Changing the current tracer clears + the ring buffer content as well as the "snapshot" buffer. available_tracers: @@ -124,9 +125,13 @@ of ftrace. Here is a list of some of the key files: trace: This file holds the output of the trace in a human - readable format (described below). Note, tracing is temporarily - disabled when the file is open for reading. Once all readers - are closed, tracing is re-enabled. + readable format (described below). Opening this file for + writing with the O_TRUNC flag clears the ring buffer content. + Note, this file is not a consumer. If tracing is off + (no tracer running, or tracing_on is zero), it will produce + the same output each time it is read. When tracing is on, + it may produce inconsistent results as it tries to read + the entire buffer without consuming it. trace_pipe: @@ -140,9 +145,7 @@ of ftrace. Here is a list of some of the key files: will not be read again with a sequential read. The "trace" file is static, and if the tracer is not adding more data, it will display the same - information every time it is read. Unlike the - "trace" file, opening this file for reading will not - temporarily disable tracing. + information every time it is read. trace_options: @@ -177,6 +180,21 @@ of ftrace. Here is a list of some of the key files: Only active when the file contains a number greater than 0. (in microseconds) + buffer_percent: + + This is the watermark for how much the ring buffer needs to be filled + before a waiter is woken up. That is, if an application calls a + blocking read syscall on one of the per_cpu trace_pipe_raw files, it + will block until the given amount of data specified by buffer_percent + is in the ring buffer before it wakes the reader up. This also + controls how the splice system calls are blocked on this file:: + + 0 - means to wake up as soon as there is any data in the ring buffer. + 50 - means to wake up when roughly half of the ring buffer sub-buffers + are full. + 100 - means to block until the ring buffer is totally full and is + about to start overwriting the older data. + buffer_size_kb: This sets or displays the number of kilobytes each CPU @@ -185,7 +203,8 @@ of ftrace. Here is a list of some of the key files: CPU buffer and not total size of all buffers. The trace buffers are allocated in pages (blocks of memory that the kernel uses for allocation, usually 4 KB in size). - If the last page allocated has room for more bytes + A few extra pages may be allocated to accommodate buffer management + meta-data. If the last page allocated has room for more bytes than requested, the rest of the page will be used, making the actual allocation bigger than requested or shown. ( Note, the size may not be a multiple of the page size @@ -199,6 +218,27 @@ of ftrace. Here is a list of some of the key files: This displays the total combined size of all the trace buffers. + buffer_subbuf_size_kb: + + This sets or displays the sub buffer size. The ring buffer is broken up + into several same size "sub buffers". An event can not be bigger than + the size of the sub buffer. Normally, the sub buffer is the size of the + architecture's page (4K on x86). The sub buffer also contains meta data + at the start which also limits the size of an event. That means when + the sub buffer is a page size, no event can be larger than the page + size minus the sub buffer meta data. + + Note, the buffer_subbuf_size_kb is a way for the user to specify the + minimum size of the subbuffer. The kernel may make it bigger due to the + implementation details, or simply fail the operation if the kernel can + not handle the request. + + Changing the sub buffer size allows for events to be larger than the + page size. + + Note: When changing the sub-buffer size, tracing is stopped and any + data in the ring buffer and the snapshot buffer will be discarded. + free_buffer: If a process is performing tracing, and the ring buffer should be @@ -235,7 +275,7 @@ of ftrace. Here is a list of some of the key files: This interface also allows for commands to be used. See the "Filter commands" section for more details. - As a speed up, since processing strings can't be quite expensive + As a speed up, since processing strings can be quite expensive and requires a check of all functions registered to tracing, instead an index can be written into this file. A number (starting with "1") written will instead select the same corresponding at the line position @@ -259,6 +299,20 @@ of ftrace. Here is a list of some of the key files: traced by the function tracer as well. This option will also cause PIDs of tasks that exit to be removed from the file. + set_ftrace_notrace_pid: + + Have the function tracer ignore threads whose PID are listed in + this file. + + If the "function-fork" option is set, then when a task whose + PID is listed in this file forks, the child's PID will + automatically be added to this file, and the child will not be + traced by the function tracer as well. This option will also + cause PIDs of tasks that exit to be removed from the file. + + If a PID is in both this file and "set_ftrace_pid", then this + file takes precedence, and the thread will not be traced. + set_event_pid: Have the events only trace a task with a PID listed in this file. @@ -270,6 +324,19 @@ of ftrace. Here is a list of some of the key files: cause the PIDs of tasks to be removed from this file when the task exits. + set_event_notrace_pid: + + Have the events not trace a task with a PID listed in this file. + Note, sched_switch and sched_wakeup will trace threads not listed + in this file, even if a thread's PID is in the file if the + sched_switch or sched_wakeup events also trace a thread that should + be traced. + + To have the PIDs of children of tasks with their PID in this file + added on fork, enable the "event-fork" option. That option will also + cause the PIDs of tasks to be removed from this file when the task + exits. + set_graph_function: Functions listed in this file will cause the function graph @@ -293,6 +360,12 @@ of ftrace. Here is a list of some of the key files: "set_graph_function", or "set_graph_notrace". (See the section "dynamic ftrace" below for more details.) + available_filter_functions_addrs: + + Similar to available_filter_functions, but with address displayed + for each function. The displayed address is the patch-site address + and can differ from /proc/kallsyms address. + dyn_ftrace_total_info: This file is for debugging purposes. The number of functions that @@ -319,15 +392,40 @@ of ftrace. Here is a list of some of the key files: an 'I' will be displayed on the same line as the function that can be overridden. + If a non ftrace trampoline is attached (BPF) a 'D' will be displayed. + Note, normal ftrace trampolines can also be attached, but only one + "direct" trampoline can be attached to a given function at a time. + + Some architectures can not call direct trampolines, but instead have + the ftrace ops function located above the function entry point. In + such cases an 'O' will be displayed. + + If a function had either the "ip modify" or a "direct" call attached to + it in the past, a 'M' will be shown. This flag is never cleared. It is + used to know if a function was every modified by the ftrace infrastructure, + and can be used for debugging. + If the architecture supports it, it will also show what callback is being directly called by the function. If the count is greater than 1 it most likely will be ftrace_ops_list_func(). - If the callback of the function jumps to a trampoline that is - specific to a the callback and not the standard trampoline, + If the callback of a function jumps to a trampoline that is + specific to the callback and which is not the standard trampoline, its address will be printed as well as the function that the trampoline calls. + touched_functions: + + This file contains all the functions that ever had a function callback + to it via the ftrace infrastructure. It has the same format as + enabled_functions but shows all functions that have every been + traced. + + To see any function that has every been modified by "ip modify" or a + direct trampoline, one can perform the following command: + + grep ' M ' /sys/kernel/tracing/touched_functions + function_profile_enabled: When set it will enable all functions with either the function @@ -345,11 +443,11 @@ of ftrace. Here is a list of some of the key files: kprobe_events: - Enable dynamic trace points. See kprobetrace.txt. + Enable dynamic trace points. See kprobetrace.rst. kprobe_profile: - Dynamic trace points stats. See kprobetrace.txt. + Dynamic trace points stats. See kprobetrace.rst. max_graph_depth: @@ -382,7 +480,7 @@ of ftrace. Here is a list of some of the key files: By default, 128 comms are saved (see "saved_cmdlines" above). To increase or decrease the amount of comms that are cached, echo - in a the number of comms to cache, into this file. + the number of comms to cache into this file. saved_tgids: @@ -486,10 +584,25 @@ of ftrace. Here is a list of some of the key files: processing should be able to handle them. See comments in the ktime_get_boot_fast_ns() function for more information. + tai: + This is the tai clock (CLOCK_TAI) and is derived from the wall- + clock time. However, this clock does not experience + discontinuities and backwards jumps caused by NTP inserting leap + seconds. Since the clock access is designed for use in tracing, + side effects are possible. The clock access may yield wrong + readouts in case the internal TAI offset is updated e.g., caused + by setting the system time or using adjtimex() with an offset. + These effects are rare and post processing should be able to + handle them. See comments in the ktime_get_tai_fast_ns() + function for more information. + To set a clock, simply echo the clock name into this file:: # echo global > trace_clock + Setting a clock clears the ring buffer content as well as the + "snapshot" buffer. + trace_marker: This is a very useful file for synchronizing user space @@ -518,7 +631,7 @@ of ftrace. Here is a list of some of the key files: start:: - trace_fd = open("trace_marker", WR_ONLY); + trace_fd = open("trace_marker", O_WRONLY); Note: Writing into the trace_marker file can also initiate triggers that are written into /sys/kernel/tracing/events/ftrace/print/trigger @@ -527,14 +640,14 @@ of ftrace. Here is a list of some of the key files: trace_marker_raw: - This is similar to trace_marker above, but is meant for for binary data + This is similar to trace_marker above, but is meant for binary data to be written to it, where a tool can be used to parse the data from trace_pipe_raw. uprobe_events: Add dynamic tracepoints in programs. - See uprobetracer.txt + See uprobetracer.rst uprobe_profile: @@ -555,19 +668,19 @@ of ftrace. Here is a list of some of the key files: files at various levels that can enable the tracepoints when a "1" is written to them. - See events.txt for more information. + See events.rst for more information. set_event: By echoing in the event into this file, will enable that event. - See events.txt for more information. + See events.rst for more information. available_events: A list of events that can be enabled in tracing. - See events.txt for more information. + See events.rst for more information. timestamp_mode: @@ -784,10 +897,10 @@ Error conditions The extended error information and usage takes the form shown in this example:: - # echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger + # echo xxx > /sys/kernel/tracing/events/sched/sched_wakeup/trigger echo: write error: Invalid argument - # cat /sys/kernel/debug/tracing/error_log + # cat /sys/kernel/tracing/error_log [ 5348.887237] location: error: Couldn't yyy: zzz Command: xxx ^ @@ -797,7 +910,7 @@ Error conditions To clear the error log, echo the empty string into it:: - # echo > /sys/kernel/debug/tracing/error_log + # echo > /sys/kernel/tracing/error_log Examples of using the tracer ---------------------------- @@ -981,6 +1094,7 @@ To see what is available, simply cat the file:: nohex nobin noblock + nofields trace_printk annotate nouserstacktrace @@ -1064,6 +1178,11 @@ Here are the available options: block When set, reading trace_pipe will not block when polled. + fields + Print the fields as described by their types. This is a better + option than using hex, bin or raw, as it gives a better parsing + of the content of the event. + trace_printk Can disable trace_printk() from writing into the buffer. @@ -1119,6 +1238,18 @@ Here are the available options: the trace displays additional information about the latency, as described in "Latency trace format". + pause-on-trace + When set, opening the trace file for read, will pause + writing to the ring buffer (as if tracing_on was set to zero). + This simulates the original behavior of the trace file. + When the file is closed, tracing will be enabled again. + + hash-ptr + When set, "%p" in the event printk format displays the + hashed pointer value instead of real address. + This will be useful if you want to find out which hashed + value is corresponding to the real value in trace log. + record-cmd When any event or tracer is enabled, a hook is enabled in the sched_switch trace point to fill comm cache @@ -1170,6 +1301,8 @@ Here are the available options: tasks fork. Also, when tasks with PIDs in set_event_pid exit, their PIDs will be removed from the file. + This affects PIDs listed in set_event_notrace_pid as well. + function-trace The latency tracers will enable function tracing if this option is enabled (default it is). When @@ -1184,6 +1317,8 @@ Here are the available options: set_ftrace_pid exit, their PIDs will be removed from the file. + This affects PIDs in set_ftrace_notrace_pid as well. + display-graph When set, the latency tracers (irqsoff, wakeup, etc) will use function graph tracing instead of function tracing. @@ -1266,6 +1401,19 @@ Options for function_graph tracer: only a closing curly bracket "}" is displayed for the return of a function. + funcgraph-retval + When set, the return value of each traced function + will be printed after an equal sign "=". By default + this is off. + + funcgraph-retval-hex + When set, the return value will always be printed + in hexadecimal format. If the option is not set and + the return value is an error code, it will be printed + in signed decimal format; otherwise it will also be + printed in hexadecimal format. By default, this option + is off. + sleep-time When running function graph tracer, to include the time a task schedules out in its function. @@ -1350,7 +1498,7 @@ an example:: => x86_64_start_reservations => x86_64_start_kernel -Here we see that that we had a latency of 16 microseconds (which is +Here we see that we had a latency of 16 microseconds (which is very good). The _raw_spin_lock_irq in run_timer_softirq disabled interrupts. The difference between the 16 and the displayed timestamp 25us occurred because the clock was incremented @@ -1409,7 +1557,7 @@ function-trace, we get a much larger output:: => __blk_run_queue_uncond => __blk_run_queue => blk_queue_bio - => generic_make_request + => submit_bio_noacct => submit_bio => submit_bh => __ext3_get_inode_loc @@ -1480,7 +1628,7 @@ display-graph option:: => remove_vma => exit_mmap => mmput - => flush_old_exec + => begin_new_exec => load_elf_binary => search_binary_handler => __do_execve_file.isra.32 @@ -1694,7 +1842,7 @@ tracers. => __blk_run_queue_uncond => __blk_run_queue => blk_queue_bio - => generic_make_request + => submit_bio_noacct => submit_bio => submit_bh => ext3_bread @@ -2120,6 +2268,8 @@ periodically make a CPU constantly busy with interrupts disabled. # cat trace # tracer: hwlat # + # entries-in-buffer/entries-written: 13/13 #P:8 + # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq @@ -2127,12 +2277,18 @@ periodically make a CPU constantly busy with interrupts disabled. # ||| / delay # TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | - <...>-3638 [001] d... 19452.055471: #1 inner/outer(us): 12/14 ts:1499801089.066141940 - <...>-3638 [003] d... 19454.071354: #2 inner/outer(us): 11/9 ts:1499801091.082164365 - <...>-3638 [002] dn.. 19461.126852: #3 inner/outer(us): 12/9 ts:1499801098.138150062 - <...>-3638 [001] d... 19488.340960: #4 inner/outer(us): 8/12 ts:1499801125.354139633 - <...>-3638 [003] d... 19494.388553: #5 inner/outer(us): 8/12 ts:1499801131.402150961 - <...>-3638 [003] d... 19501.283419: #6 inner/outer(us): 0/12 ts:1499801138.297435289 nmi-total:4 nmi-count:1 + <...>-1729 [001] d... 678.473449: #1 inner/outer(us): 11/12 ts:1581527483.343962693 count:6 + <...>-1729 [004] d... 689.556542: #2 inner/outer(us): 16/9 ts:1581527494.889008092 count:1 + <...>-1729 [005] d... 714.756290: #3 inner/outer(us): 16/16 ts:1581527519.678961629 count:5 + <...>-1729 [001] d... 718.788247: #4 inner/outer(us): 9/17 ts:1581527523.889012713 count:1 + <...>-1729 [002] d... 719.796341: #5 inner/outer(us): 13/9 ts:1581527524.912872606 count:1 + <...>-1729 [006] d... 844.787091: #6 inner/outer(us): 9/12 ts:1581527649.889048502 count:2 + <...>-1729 [003] d... 849.827033: #7 inner/outer(us): 18/9 ts:1581527654.889013793 count:1 + <...>-1729 [007] d... 853.859002: #8 inner/outer(us): 9/12 ts:1581527658.889065736 count:1 + <...>-1729 [001] d... 855.874978: #9 inner/outer(us): 9/11 ts:1581527660.861991877 count:1 + <...>-1729 [001] d... 863.938932: #10 inner/outer(us): 9/11 ts:1581527668.970010500 count:1 nmi-total:7 nmi-count:1 + <...>-1729 [007] d... 878.050780: #11 inner/outer(us): 9/12 ts:1581527683.385002600 count:1 nmi-total:5 nmi-count:1 + <...>-1729 [007] d... 886.114702: #12 inner/outer(us): 9/12 ts:1581527691.385001600 count:1 The above output is somewhat the same in the header. All events will have @@ -2142,7 +2298,7 @@ interrupts disabled 'd'. Under the FUNCTION title there is: This is the count of events recorded that were greater than the tracing_threshold (See below). - inner/outer(us): 12/14 + inner/outer(us): 11/11 This shows two numbers as "inner latency" and "outer latency". The test runs in a loop checking a timestamp twice. The latency detected within @@ -2150,11 +2306,15 @@ interrupts disabled 'd'. Under the FUNCTION title there is: after the previous timestamp and the next timestamp in the loop is the "outer latency". - ts:1499801089.066141940 + ts:1581527483.343962693 + + The absolute timestamp that the first latency was recorded in the window. - The absolute timestamp that the event happened. + count:6 - nmi-total:4 nmi-count:1 + The number of times a latency was detected during the window. + + nmi-total:7 nmi-count:1 On architectures that support it, if an NMI comes in during the test, the time spent in NMI is reported in "nmi-total" (in @@ -2380,11 +2540,10 @@ Or this simple script! #!/bin/bash tracefs=`sed -ne 's/^tracefs \(.*\) tracefs.*/\1/p' /proc/mounts` - echo nop > $tracefs/tracing/current_tracer - echo 0 > $tracefs/tracing/tracing_on - echo $$ > $tracefs/tracing/set_ftrace_pid - echo function > $tracefs/tracing/current_tracer - echo 1 > $tracefs/tracing/tracing_on + echo 0 > $tracefs/tracing_on + echo $$ > $tracefs/set_ftrace_pid + echo function > $tracefs/current_tracer + echo 1 > $tracefs/tracing_on exec "$@" @@ -2451,7 +2610,7 @@ want, depending on your needs. - The cpu number on which the function executed is default enabled. It is sometimes better to only trace one cpu (see - tracing_cpu_mask file) or you might sometimes see unordered + tracing_cpumask file) or you might sometimes see unordered function calls while cpu tracing switch. - hide: echo nofuncgraph-cpu > trace_options @@ -2600,6 +2759,119 @@ It is default disabled. 0) 1.757 us | } /* kmem_cache_free() */ 0) 2.861 us | } /* putname() */ +The return value of each traced function can be displayed after +an equal sign "=". When encountering system call failures, it +can be very helpful to quickly locate the function that first +returns an error code. + + - hide: echo nofuncgraph-retval > trace_options + - show: echo funcgraph-retval > trace_options + + Example with funcgraph-retval:: + + 1) | cgroup_migrate() { + 1) 0.651 us | cgroup_migrate_add_task(); /* = 0xffff93fcfd346c00 */ + 1) | cgroup_migrate_execute() { + 1) | cpu_cgroup_can_attach() { + 1) | cgroup_taskset_first() { + 1) 0.732 us | cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */ + 1) 1.232 us | } /* cgroup_taskset_first = 0xffff93fc8fb20000 */ + 1) 0.380 us | sched_rt_can_attach(); /* = 0x0 */ + 1) 2.335 us | } /* cpu_cgroup_can_attach = -22 */ + 1) 4.369 us | } /* cgroup_migrate_execute = -22 */ + 1) 7.143 us | } /* cgroup_migrate = -22 */ + +The above example shows that the function cpu_cgroup_can_attach +returned the error code -22 firstly, then we can read the code +of this function to get the root cause. + +When the option funcgraph-retval-hex is not set, the return value can +be displayed in a smart way. Specifically, if it is an error code, +it will be printed in signed decimal format, otherwise it will +printed in hexadecimal format. + + - smart: echo nofuncgraph-retval-hex > trace_options + - hexadecimal: echo funcgraph-retval-hex > trace_options + + Example with funcgraph-retval-hex:: + + 1) | cgroup_migrate() { + 1) 0.651 us | cgroup_migrate_add_task(); /* = 0xffff93fcfd346c00 */ + 1) | cgroup_migrate_execute() { + 1) | cpu_cgroup_can_attach() { + 1) | cgroup_taskset_first() { + 1) 0.732 us | cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */ + 1) 1.232 us | } /* cgroup_taskset_first = 0xffff93fc8fb20000 */ + 1) 0.380 us | sched_rt_can_attach(); /* = 0x0 */ + 1) 2.335 us | } /* cpu_cgroup_can_attach = 0xffffffea */ + 1) 4.369 us | } /* cgroup_migrate_execute = 0xffffffea */ + 1) 7.143 us | } /* cgroup_migrate = 0xffffffea */ + +At present, there are some limitations when using the funcgraph-retval +option, and these limitations will be eliminated in the future: + +- Even if the function return type is void, a return value will still + be printed, and you can just ignore it. + +- Even if return values are stored in multiple registers, only the + value contained in the first register will be recorded and printed. + To illustrate, in the x86 architecture, eax and edx are used to store + a 64-bit return value, with the lower 32 bits saved in eax and the + upper 32 bits saved in edx. However, only the value stored in eax + will be recorded and printed. + +- In certain procedure call standards, such as arm64's AAPCS64, when a + type is smaller than a GPR, it is the responsibility of the consumer + to perform the narrowing, and the upper bits may contain UNKNOWN values. + Therefore, it is advisable to check the code for such cases. For instance, + when using a u8 in a 64-bit GPR, bits [63:8] may contain arbitrary values, + especially when larger types are truncated, whether explicitly or implicitly. + Here are some specific cases to illustrate this point: + + **Case One**: + + The function narrow_to_u8 is defined as follows:: + + u8 narrow_to_u8(u64 val) + { + // implicitly truncated + return val; + } + + It may be compiled to:: + + narrow_to_u8: + < ... ftrace instrumentation ... > + RET + + If you pass 0x123456789abcdef to this function and want to narrow it, + it may be recorded as 0x123456789abcdef instead of 0xef. + + **Case Two**: + + The function error_if_not_4g_aligned is defined as follows:: + + int error_if_not_4g_aligned(u64 val) + { + if (val & GENMASK(31, 0)) + return -EINVAL; + + return 0; + } + + It could be compiled to:: + + error_if_not_4g_aligned: + CBNZ w0, .Lnot_aligned + RET // bits [31:0] are zero, bits + // [63:32] are UNKNOWN + .Lnot_aligned: + MOV x0, #-EINVAL + RET + + When passing 0x2_0000_0000 to it, the return value may be recorded as + 0x2_0000_0000 instead of 0. + You can put some comments on specific functions by using trace_printk() For example, if you want to put a comment inside the __might_sleep() function, you just have to include @@ -2700,7 +2972,7 @@ listed in: put_prev_task_idle kmem_cache_create pick_next_task_rt - get_online_cpus + cpus_read_lock pick_next_task_fair mutex_lock [...] @@ -2867,7 +3139,7 @@ Produces:: bash-1994 [000] .... 4342.324898: ima_get_action <-process_measurement bash-1994 [000] .... 4342.324898: ima_match_policy <-ima_get_action bash-1994 [000] .... 4342.324899: do_truncate <-do_last - bash-1994 [000] .... 4342.324899: should_remove_suid <-do_truncate + bash-1994 [000] .... 4342.324899: setattr_should_drop_suidgid <-do_truncate bash-1994 [000] .... 4342.324899: notify_change <-do_truncate bash-1994 [000] .... 4342.324900: current_fs_time <-notify_change bash-1994 [000] .... 4342.324900: current_kernel_time <-current_fs_time @@ -3309,7 +3581,7 @@ one of the latency tracers, you will get the following results. Instances --------- -In the tracefs tracing directory is a directory called "instances". +In the tracefs tracing directory, there is a directory called "instances". This directory can have new directories created inside of it using mkdir, and removing directories with rmdir. The directory created with mkdir in this directory will already contain files and other @@ -3324,7 +3596,7 @@ directories after it is created. As you can see, the new directory looks similar to the tracing directory itself. In fact, it is very similar, except that the buffer and -events are agnostic from the main director, or from any other +events are agnostic from the main directory, or from any other instances that are created. The files in the new directory work just like the files with the @@ -3437,7 +3709,7 @@ directories, the rmdir will fail with EBUSY. Stack trace ----------- Since the kernel has a fixed sized stack, it is important not to -waste it in functions. A kernel developer must be conscience of +waste it in functions. A kernel developer must be conscious of what they allocate on the stack. If they add too much, the system can be in danger of a stack overflow, and corruption will occur, usually leading to a system panic. |