2e854bccc6
see discussion from after https://github.com/redis/redis/pull/12453 was merged ---- This PR replaces signals that are not considered async-signal-safe (AS-safe) with safe calls. #### **1. serverLog() and serverLogFromHandler()** `serverLog` uses unsafe calls. It was decided that we will **avoid** `serverLog` calls by the signal handlers when: * The signal is not fatal, such as SIGALRM. In these cases, we prefer using `serverLogFromHandler` which is the safe version of `serverLog`. Note they have different prompts: `serverLog`: `62220:M 26 Oct 2023 14:39:04.526 # <msg>` `serverLogFromHandler`: `62220:signal-handler (1698331136) <msg>` * The code was added recently. Calls to `serverLog` by the signal handler have been there ever since Redis exists and it hasn't caused problems so far. To avoid regression, from now we should use `serverLogFromHandler` #### **2. `snprintf` `fgets` and `strtoul`(base = 16) --------> `_safe_snprintf`, `fgets_async_signal_safe`, `string_to_hex`** The safe version of `snprintf` was taken from [here](8cfc4ca5e7/src/mc_util.c (L754)) #### **3. fopen(), fgets(), fclose() --------> open(), read(), close()** #### **4. opendir(), readdir(), closedir() --------> open(), syscall(SYS_getdents64), close()** #### **5. Threads_mngr sync mechanisms** * waiting for the thread to generate stack trace: semaphore --------> busy-wait * `globals_rw_lock` was removed: as we are not using malloc and the semaphore anymore we don't need to protect `ThreadsManager_cleanups`. #### **6. Stacktraces buffer** The initial problem was that we were not able to safely call malloc within the signal handler. To solve that we created a buffer on the stack of `writeStacktraces` and saved it in a global pointer, assuming that under normal circumstances, the function `writeStacktraces` would complete before any thread attempted to write to it. However, **if threads lag behind, they might access this global pointer after it no longer belongs to the `writeStacktraces` stack, potentially corrupting memory.** To address this, various solutions were discussed [here](https://github.com/redis/redis/pull/12658#discussion_r1390442896) Eventually, we decided to **create a pipe** at server startup that will remain valid as long as the process is alive. We chose this solution due to its minimal memory usage, and since `write()` and `read()` are atomic operations. It ensures that stack traces from different threads won't mix. **The stacktraces collection process is now as follows:** * Cleaning the pipe to eliminate writes of late threads from previous runs. * Each thread writes to the pipe its stacktrace * Waiting for all the threads to mark completion or until a timeout (2 sec) is reached * Reading from the pipe to print the stacktraces. #### **7. Changes that were considered and eventually were dropped** * replace watchdog timer with a POSIX timer: according to [settimer man](https://linux.die.net/man/2/setitimer) > POSIX.1-2008 marks getitimer() and setitimer() obsolete, recommending the use of the POSIX timers API ([timer_gettime](https://linux.die.net/man/2/timer_gettime)(2), [timer_settime](https://linux.die.net/man/2/timer_settime)(2), etc.) instead. However, although it is supposed to conform to POSIX std, POSIX timers API is not supported on Mac. You can take a look here at the Linux implementation: [here](c7562ee135) To avoid messing up the code, and uncertainty regarding compatibility, it was decided to drop it for now. * avoid using sds (uses malloc) in logConfigDebugInfo It was considered to print config info instead of using sds, however apparently, `logConfigDebugInfo` does more than just print the sds, so it was decided this fix is out of this issue scope. #### **8. fix Signal mask check** The check `signum & sig_mask` intended to indicate whether the signal is blocked by the thread was incorrect. Actually, the bit position in the signal mask corresponds to the signal number. We fixed this by changing the condition to: `sig_mask & (1L << (sig_num - 1))` #### **9. Unrelated changes** both `fork.tcl `and `util.tcl` implemented a function called `count_log_message` expecting different parameters. This caused confusion when trying to run daily tests with additional test parameters to run a specific test. The `count_log_message` in `fork.tcl` was removed and the calls were replaced with calls to `count_log_message` located in `util.tcl` --------- Co-authored-by: Ozan Tezcan <ozantezcan@gmail.com> Co-authored-by: Oran Agra <oran@redislabs.com>
70 lines
2.9 KiB
C
70 lines
2.9 KiB
C
/*
|
|
* Copyright (c) 2021, Redis Ltd.
|
|
* All rights reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions are met:
|
|
*
|
|
* * Redistributions of source code must retain the above copyright notice,
|
|
* this list of conditions and the following disclaimer.
|
|
* * Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
* * Neither the name of Redis nor the names of its contributors may be used
|
|
* to endorse or promote products derived from this software without
|
|
* specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
|
|
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
|
|
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
* POSSIBILITY OF SUCH DAMAGE.
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include "fmacros.h"
|
|
|
|
#include <sys/types.h>
|
|
#include <unistd.h>
|
|
|
|
/** This is an API to invoke callback on a list of threads using a user defined signal handler.
|
|
* NOTE: This is API is only supported only in linux systems.
|
|
* Calling the functions below on any other system does nothing.
|
|
*/
|
|
|
|
#define THREADS_SIGNAL SIGUSR2
|
|
|
|
/* Callback signature */
|
|
typedef void(*run_on_thread_cb)(void);
|
|
|
|
/* Register the process to THREADS_SIGNAL */
|
|
void ThreadsManager_init(void);
|
|
|
|
/** @brief Invoke callback by each thread in tids.
|
|
*
|
|
* @param tids An array of threads that need to invoke callback.
|
|
* @param tids_len The number of threads in @param tids.
|
|
* @param callback A callback to be invoked by each thread in @param tids.
|
|
*
|
|
* NOTES:
|
|
* It is assumed that all the threads don't block or ignore THREADS_SIGNAL.
|
|
*
|
|
* It is safe to include the calling thread in @param tids. However, be aware that subsequent tids will
|
|
* not be signaled until the calling thread returns from the callback invocation.
|
|
* Hence, it is recommended to place the calling thread last in @param tids.
|
|
*
|
|
* The function returns only when @param tids_len threads have returned from @param callback, or when we reached timeout.
|
|
*
|
|
* @return 1 if successful, 0 If ThreadsManager_runOnThreads is already in the middle of execution.
|
|
*
|
|
**/
|
|
|
|
int ThreadsManager_runOnThreads(pid_t *tids, size_t tids_len, run_on_thread_cb callback);
|