From: compudj Date: Wed, 8 Mar 2006 04:35:33 +0000 (+0000) Subject: futex X-Git-Tag: v0.12.20~1876 X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=47d7d576a49691703007b6534a5d2658b15eff66;p=lttv.git futex git-svn-id: http://ltt.polymtl.ca/svn@1613 04897980-b3bd-0310-b5e0-8ef037075253 --- diff --git a/usertrace-fast/ltt-usertrace-fast.c b/usertrace-fast/ltt-usertrace-fast.c index c809aff0..5f8c5e08 100644 --- a/usertrace-fast/ltt-usertrace-fast.c +++ b/usertrace-fast/ltt-usertrace-fast.c @@ -58,6 +58,8 @@ #include #include #include +#include +#include #include //for get_cycles() @@ -116,6 +118,119 @@ static void handler_sigalarm(int signo) alarm(3); } +/* Do a buffer switch. Don't switch if buffer is completely empty */ +static void flush_buffer(struct ltt_buf *ltt_buf) +{ + + +} + +static inline int ltt_buffer_get(struct ltt_buf *ltt_buf, + unsigned int *offset) +{ + unsigned int consumed_old, consumed_idx; + consumed_old = atomic_read(<t_buf->consumed); + consumed_idx = SUBBUF_INDEX(consumed_old, ltt_buf); + + if(atomic_read(<t_buf->commit_count[consumed_idx]) + != atomic_read(<t_buf->reserve_count[consumed_idx])) { + return -EAGAIN; + } + if((SUBBUF_TRUNC(atomic_read(<t_buf->offset), ltt_buf) + -SUBBUF_TRUNC(consumed_old, ltt_buf)) == 0) { + return -EAGAIN; + } + + *offset = consumed_old; + + return 0; +} + +static inline int ltt_buffer_put(struct ltt_buf *ltt_buf, + unsigned int offset) +{ + unsigned int consumed_old, consumed_new; + int ret; + + consumed_old = offset; + consumed_new = SUBBUF_ALIGN(consumed_old, ltt_buf); + if(atomic_cmpxchg(<t_buf->consumed, consumed_old, consumed_new) + != consumed_old) { + /* We have been pushed by the writer : the last buffer read _is_ + * corrupted! + * It can also happen if this is a buffer we never got. */ + return -EIO; + } else { + if(atomic_read(<t_buf->full) == 1) { + /* tell the client that buffer is now unfull */ + ret = futex(<t_buf->full, FUTEX_WAKE, 1, NULL, NULL, 0); + if(ret != 1) { + printf("LTT warning : race condition : writer not waiting or too many writers\n"); + } + atomic_set(<t_buf->full, 0); + } + } +} + +/* In the writer : + * + * if(buffer full condition) { + * put myself in the wait queue + * ltt_buf->full = 1; + * schedule + * } + *{ + if(buffer_is_full) { + atomic_set(<t_buf->full, 1); + ret = futex(<t_buf->full, 1, NULL, NULL, 0); + } +} + + */ + +static int read_subbuffer(struct ltt_buf *ltt_buf, int fd) +{ + int err; + printf("LTT read buffer\n"); + + + err = ltt_buffer_get(&shared_trace_info->channel.cpu, &consumed_old); + if(err != -EAGAIN && err != 0) { + printf("LTT Reserving sub buffer failed\n"); + goto get_error; + } + + err = TEMP_FAILURE_RETRY(write(fd, + ltt_buf->start + + (consumed_old & ((ltt_buf->alloc_size)-1)), + ltt_buf->subbuf_size)); + + if(err < 0) { + perror("Error in writing to file"); + goto write_error; + } +#if 0 + err = fsync(pair->trace); + if(err < 0) { + ret = errno; + perror("Error in writing to file"); + goto write_error; + } +#endif //0 +write_error: + err = ltt_buffer_put(&shared_trace_info->channel.cpu, consumed_old); + + if(err != 0) { + if(err == -EIO) { + perror("Reader has been pushed by the writer, last subbuffer corrupted."); + /* FIXME : we may delete the last written buffer if we wish. */ + } + goto get_error; + } + +get_error: + return err; +} /* This function is called by ltt_rw_init which has signals blocked */ static void ltt_usertrace_fast_daemon(struct ltt_trace_info *shared_trace_info, @@ -187,12 +302,28 @@ static void ltt_usertrace_fast_daemon(struct ltt_trace_info *shared_trace_info, if(traced_pid == 0) break; /* parent died */ if(parent_exited) break; printf("LTT Doing a buffer switch read. pid is : %lu\n", getpid()); - //printf("Test parent. pid is : %lu, ppid is %lu\n", getpid(), getppid()); + + do { + ret = read_buffer(&shared_trace_info->channel.cpu, fd_cpu); + } while(ret == 0); + + do { + ret = read_buffer(&shared_trace_info->channel.facilities, fd_fac); + } while(ret == 0); } /* Buffer force switch (flush) */ - //TODO - + flush_buffer(&shared_trace_info->channel.cpu); + do { + ret = read_buffer(&shared_trace_info->channel.cpu, fd_cpu); + } while(ret == 0); + + + flush_buffer(&shared_trace_info->channel.facilities); + do { + ret = read_buffer(&shared_trace_info->channel.facilities, fd_fac); + } while(ret == 0); + close(fd_fac); close(fd_cpu); @@ -222,6 +353,14 @@ void ltt_rw_init(void) shared_trace_info = mmap(0, sizeof(*thread_trace_info), PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, 0, 0); memset(shared_trace_info, 0, sizeof(*shared_trace_info)); + /* Tricky semaphore : is in a shared memory space, so it's ok for a fast + * mutex (futex). */ + atomic_set(&shared_trace_info->channel.facilities.full, 0); + shared_trace_info->channel.facilities.alloc_size = LTT_BUF_SIZE_FACILITIES; + shared_trace_info->channel.facilities.subbuf_size = LTT_SUBBUF_SIZE_FACILITIES; + atomic_set(&shared_trace_info->channel.cpu.full, 0); + shared_trace_info->channel.cpu.alloc_size = LTT_BUF_SIZE_CPU; + shared_trace_info->channel.cpu.subbuf_size = LTT_SUBBUF_SIZE_CPU; shared_trace_info->init = 1; /* Disable signals */ diff --git a/usertrace-fast/ltt-usertrace-fast.h b/usertrace-fast/ltt-usertrace-fast.h index fcd67e53..811a2537 100644 --- a/usertrace-fast/ltt-usertrace-fast.h +++ b/usertrace-fast/ltt-usertrace-fast.h @@ -12,34 +12,56 @@ #include #include -#ifndef LTT_BUF_SIZE_CPU -#define LTT_BUF_SIZE_CPU 1048576 + +#ifndef LTT_N_SUBBUFS +#define LTT_N_SUBBUFS 2 +#endif //LTT_N_SUBBUFS + +#ifndef LTT_SUBBUF_SIZE_CPU +#define LTT_SUBBUF_SIZE_CPU 1048576 #endif //LTT_BUF_SIZE_CPU -#ifndef LTT_BUF_SIZE_FACILITIES -#define LTT_BUF_SIZE_FACILITIES 4096 +#define LTT_BUF_SIZE_CPU (LTT_SUBBUF_SIZE_CPU * LTT_N_SUBBUFS) + +#ifndef LTT_SUBBUF_SIZE_FACILITIES +#define LTT_SUBBUF_SIZE_FACILITIES 4096 #endif //LTT_BUF_SIZE_FACILITIES +#define LTT_BUF_SIZE_FACILITIES (LTT_SUBBUF_SIZE_FACILITIES * LTT_N_SUBBUFS) + #ifndef LTT_USERTRACE_ROOT #define LTT_USERTRACE_ROOT "/tmp/ltt-usertrace" #endif //LTT_USERTRACE_ROOT + +/* Buffer offset macros */ + +#define BUFFER_OFFSET(offset, buf) (offset & (buf->alloc_size-1)) +#define SUBBUF_OFFSET(offset, buf) (offset & (buf->subbuf_size-1)) +#define SUBBUF_ALIGN(offset, buf) \ + (((offset) + buf->subbuf_size) & (~(buf->subbuf_size-1))) +#define SUBBUF_TRUNC(offset, buf) \ + ((offset) & (~(buf->subbuf_size-1))) +#define SUBBUF_INDEX(offset, buf) \ + (BUFFER_OFFSET(offset,buf)/buf->subbuf_size) + + struct ltt_buf { atomic_t offset; - atomic_t reserve_count; - atomic_t commit_count; + atomic_t consumed; + atomic_t reserve_count[LTT_N_SUBBUFS]; + atomic_t commit_count[LTT_N_SUBBUFS]; atomic_t events_lost; + atomic_t full; /* futex on which the writer waits : 1 : full */ + unsigned int alloc_size; + unsigned int subbuf_size; }; struct ltt_trace_info { int init; int filter; -#ifndef LTT_USE_THREADS pid_t daemon_id; -#else - pthread_t daemon_id; -#endif //LTT_USE_THREADS atomic_t nesting; struct { struct ltt_buf facilities;