On 23.06.21 г. 16:19, Steven Rostedt wrote:
On Wed, 23 Jun 2021 16:02:00 +0300 Yordan Karadzhov <y.karadz@xxxxxxxxx> wrote:I'm thinking we should invert the above. That is, have a stop instead of "keep_going", where it is false by default (when the instance is created). That's because, if we start here, and the SIGINT comes in before we get here, it keep_going might get set to false, and missed.I intentionally tried to avoid having any dependency of the initialization value of the "keep_going" flag. We have to consider the case when the user creates one instance and then calls this function multiple times in a row.If anything then, make it the first thing that gets done, and not just before the loop. That is: +int tracefs_trace_pipe_stream(int fd, struct tracefs_instance *instance, + int flags) +{ + int *keep_going = instance ? &instance->pipe_keep_going : + &top_pipe_keep_going; + const char *file = "trace_pipe"; + int brass[2], in_fd, ret = -1; + off_t data_size; *keep_going = true; + + in_fd = tracefs_instance_file_open(instance, file, O_RDONLY); + if (in_fd < 0) { + tracefs_warning("Failed to open 'trace_pipe'."); + return ret; + } + + if(pipe(brass) < 0) { + tracefs_warning("Failed to open pipe."); + goto close_file; + } + + data_size = fcntl(brass[0], F_GETPIPE_SZ); + if (data_size <= 0) { + tracefs_warning("Failed to open pipe (size=0)."); + goto close_all; + } + + *keep_going = true; And not here. + while (*keep_going) { + ret = splice(in_fd, NULL, + brass[1], NULL, + data_size, flags); + if (ret < 0) + break; + + ret = splice(brass[0], NULL, + fd, NULL, + data_size, flags); + if (ret < 0) + break; + } And I think we need to make it volatile, otherwise the compiler is free to ignore it. Because the compiler does not need to know about threads. *keep_going = true; while (*keep_going) { [ do something ] } To the compiler that is the same as: while (1) { [ do something ] } And is free to make that change when optimizing. What needs to be done is: (*(volatile bool *)keep_going) = true; and while (*(volatile bool *)keep_going) { That way the compiler knows that the value can change from outside its knowledge.
OK, I will make the changes and will send v3. Thanks a lot! Yordan
-- Steve
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