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21fbefc588
- Use READ_ONCE() and WRITE_ONCE() instead of RCU for syscall tracepoints Individual system call trace events are pseudo events attached to the raw_syscall trace events that just trace the entry and exit of all system calls. When any of these individual system call trace events get enabled, an element in an array indexed by the system call number is assigned to the trace file that defines how to trace it. When the trace event triggers, it reads this array and if the array has an element, it uses that trace file to know what to write it (the trace file defines the output format of the corresponding system call). The issue is that it uses rcu_dereference_ptr() and marks the elements of the array as using RCU. This is incorrect. There is no RCU synchronization here. The event file that is pointed to has a completely different way to make sure its freed properly. The reading of the array during the system call trace event is only to know if there is a value or not. If not, it does nothing (it means this system call isn't being traced). If it does, it uses the information to store the system call data. The RCU usage here can simply be replaced by READ_ONCE() and WRITE_ONCE() macros. - Have the system call trace events use "0x" for hex values Some system call trace events display hex values but do not have "0x" in front of it. Seeing "count: 44" can be assumed that it is 44 decimal when in actuality it is 44 hex (68 decimal). Display "0x44" instead. - Use vmalloc_array() in tracing_map_sort_entries() The function tracing_map_sort_entries() used array_size() and vmalloc() when it could have simply used vmalloc_array(). - Use for_each_online_cpu() in trace_osnoise.c() Instead of open coding for_each_cpu(cpu, cpu_online_mask), use for_each_online_cpu(). - Move the buffer field in struct trace_seq to the end The buffer field in struct trace_seq is architecture dependent in size, and caused padding for the fields after it. By moving the buffer to the end of the structure, it compacts the trace_seq structure better. - Remove redundant zeroing of cmdline_idx field in saved_cmdlines_buffer() The structure that contains cmdline_idx is zeroed by memset(), no need to explicitly zero any of its fields after that. - Use system_percpu_wq instead of system_wq in user_event_mm_remove() As system_wq is being deprecated, use the new wq. - Add cond_resched() is ftrace_module_enable() Some modules have a lot of functions (thousands of them), and the enabling of those functions can take some time. On non preemtable kernels, it was triggering a watchdog timeout. Add a cond_resched() to prevent that. - Add a BUILD_BUG_ON() to make sure PID_MAX_DEFAULT is always a power of 2 There's code that depends on PID_MAX_DEFAULT being a power of 2 or it will break. If in the future that changes, make sure the build fails to ensure that the code is fixed that depends on this. - Grab mutex_lock() before ever exiting s_start() The s_start() function is a seq_file start routine. As s_stop() is always called even if s_start() fails, and s_stop() expects the event_mutex to be held as it will always release it. That mutex must always be taken in s_start() even if that function fails. -----BEGIN PGP SIGNATURE----- iIoEABYKADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCaN/4phQccm9zdGVkdEBn b29kbWlzLm9yZwAKCRAp5XQQmuv6qpToAP4sENpZkZHFOl2PuikmAgjhB6PqiUtL LNuMDx45WygcLwD6Awy8DUlEBN6RzTPA761MSjs0+NMg16QLrhPLxWqFEgw= =nxDn -----END PGP SIGNATURE----- Merge tag 'trace-v6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing updates from Steven Rostedt: - Use READ_ONCE() and WRITE_ONCE() instead of RCU for syscall tracepoints Individual system call trace events are pseudo events attached to the raw_syscall trace events that just trace the entry and exit of all system calls. When any of these individual system call trace events get enabled, an element in an array indexed by the system call number is assigned to the trace file that defines how to trace it. When the trace event triggers, it reads this array and if the array has an element, it uses that trace file to know what to write it (the trace file defines the output format of the corresponding system call). The issue is that it uses rcu_dereference_ptr() and marks the elements of the array as using RCU. This is incorrect. There is no RCU synchronization here. The event file that is pointed to has a completely different way to make sure its freed properly. The reading of the array during the system call trace event is only to know if there is a value or not. If not, it does nothing (it means this system call isn't being traced). If it does, it uses the information to store the system call data. The RCU usage here can simply be replaced by READ_ONCE() and WRITE_ONCE() macros. - Have the system call trace events use "0x" for hex values Some system call trace events display hex values but do not have "0x" in front of it. Seeing "count: 44" can be assumed that it is 44 decimal when in actuality it is 44 hex (68 decimal). Display "0x44" instead. - Use vmalloc_array() in tracing_map_sort_entries() The function tracing_map_sort_entries() used array_size() and vmalloc() when it could have simply used vmalloc_array(). - Use for_each_online_cpu() in trace_osnoise.c() Instead of open coding for_each_cpu(cpu, cpu_online_mask), use for_each_online_cpu(). - Move the buffer field in struct trace_seq to the end The buffer field in struct trace_seq is architecture dependent in size, and caused padding for the fields after it. By moving the buffer to the end of the structure, it compacts the trace_seq structure better. - Remove redundant zeroing of cmdline_idx field in saved_cmdlines_buffer() The structure that contains cmdline_idx is zeroed by memset(), no need to explicitly zero any of its fields after that. - Use system_percpu_wq instead of system_wq in user_event_mm_remove() As system_wq is being deprecated, use the new wq. - Add cond_resched() is ftrace_module_enable() Some modules have a lot of functions (thousands of them), and the enabling of those functions can take some time. On non preemtable kernels, it was triggering a watchdog timeout. Add a cond_resched() to prevent that. - Add a BUILD_BUG_ON() to make sure PID_MAX_DEFAULT is always a power of 2 There's code that depends on PID_MAX_DEFAULT being a power of 2 or it will break. If in the future that changes, make sure the build fails to ensure that the code is fixed that depends on this. - Grab mutex_lock() before ever exiting s_start() The s_start() function is a seq_file start routine. As s_stop() is always called even if s_start() fails, and s_stop() expects the event_mutex to be held as it will always release it. That mutex must always be taken in s_start() even if that function fails. * tag 'trace-v6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: tracing: Fix lock imbalance in s_start() memory allocation failure path tracing: Ensure optimized hashing works ftrace: Fix softlockup in ftrace_module_enable tracing: replace use of system_wq with system_percpu_wq tracing: Remove redundant 0 value initialization tracing: Move buffer in trace_seq to end of struct tracing/osnoise: Use for_each_online_cpu() instead of for_each_cpu() tracing: Use vmalloc_array() to improve code tracing: Have syscall trace events show "0x" for values greater than 10 tracing: Replace syscall RCU pointer assignment with READ/WRITE_ONCE() |
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| debug | ||
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| entry | ||
| events | ||
| futex | ||
| gcov | ||
| irq | ||
| kcsan | ||
| livepatch | ||
| locking | ||
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| power | ||
| printk | ||
| rcu | ||
| sched | ||
| time | ||
| trace | ||
| unwind | ||
| .gitignore | ||
| acct.c | ||
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| audit.c | ||
| audit.h | ||
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| cpu.c | ||
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| crash_dump_dm_crypt.c | ||
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| cred.c | ||
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| Kconfig.freezer | ||
| Kconfig.hz | ||
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| Kconfig.locks | ||
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| kcov.c | ||
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| stacktrace.c | ||
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