From patchwork Fri Nov 15 13:10:39 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Robert Foley X-Patchwork-Id: 11246333 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5A24613BD for ; Fri, 15 Nov 2019 13:14:46 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 20B4C2073A for ; Fri, 15 Nov 2019 13:14:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="zcwcxRr5" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 20B4C2073A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:39104 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iVbQz-0007ul-3P for patchwork-qemu-devel@patchwork.kernel.org; Fri, 15 Nov 2019 08:14:45 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:49464) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iVbO4-0004Y2-RJ for qemu-devel@nongnu.org; Fri, 15 Nov 2019 08:11:46 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iVbO2-0004Qg-Uj for qemu-devel@nongnu.org; Fri, 15 Nov 2019 08:11:44 -0500 Received: from mail-pl1-x642.google.com ([2607:f8b0:4864:20::642]:34719) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1iVbO2-0004QQ-Mq for qemu-devel@nongnu.org; Fri, 15 Nov 2019 08:11:42 -0500 Received: by mail-pl1-x642.google.com with SMTP id h13so4662115plr.1 for ; Fri, 15 Nov 2019 05:11:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=PTGGv6BbjW5b5UzOcudWx+Llbn7h0ebnhlDgy3PCo6A=; b=zcwcxRr5s0X8XKc7odSh9d6X2Igz6nn4qO5MehiFBPBFphEawTY1mbU0scFHRm6IxI Uk6v+djcJInqvJLPFTXqiWn+0hqOBQmnVUZCK9vXBFUMykNFqh5IJP9ABgCEwJr4UH0t fmglZFV4t8GY36Y3mozJjWLJuITP8Sq7xbCrYONMOrCzXZvcr8mNmrpUHK8NzH8DWIY7 S7fR4csxVZbFPe9rOXGgl2rHZc3EThahTzhhQXndIv1cZcWxBhb+jXwH0P9laXa/FgFJ QK7rQKlMoxqXf3gPrNDkTNfE3PnjbhaczxqiNWcISZI7LsuhDg0ZjWVpbiEtfXykhuO8 asLQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=PTGGv6BbjW5b5UzOcudWx+Llbn7h0ebnhlDgy3PCo6A=; b=D3/pf5sflyhzzPjz3Lm/ITJPAALTPHE3MsFg+pQVW8BMjV0eHVUIex16z9HrPb/Yz7 mAfi+LU14Xarl0b3YSMbaj55EKqDN6/IVR/RJ+u/jeT5M7V+3htEP+oG0eDoT8BLF3JX O8nNCVNCY1NY+30xcp40jQW0MWfiTKZxSJu9ErFnYmZMzwcEqXHFYkW6rU53NBACLchK S/5rfAFZJQfYmvjx4YUaWTJWDLKc2EIPaAF0EruYUAKqStpHed4ET6KaX41I+QeNVkms 7dgElvTZnqF3mxjRqFtXVDCQg3MIfCA3LL14VH0sjPSn/f/xaJvYy/Z8jv/N2gMMtcKx N7iA== X-Gm-Message-State: APjAAAX4/QiZbP5+CWaASq8Y8KP7QuGoD31Yv+xCGwC23mKZztRndqrX /rfon+lEjZwVsVwXsBnNTCOvLqG1zOY= X-Google-Smtp-Source: APXvYqyJgv5xOdEier+OC3ZqRlUpT34KvWKfkphYJL5AfXd+22GngfHnAV0ikfbuQ3fvNjgQlfAH2A== X-Received: by 2002:a17:90a:a483:: with SMTP id z3mr18699681pjp.55.1573823501265; Fri, 15 Nov 2019 05:11:41 -0800 (PST) Received: from Rfoley-MA01.usrd.futurewei.com ([12.111.81.71]) by smtp.gmail.com with ESMTPSA id w138sm12007249pfc.68.2019.11.15.05.11.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Nov 2019 05:11:40 -0800 (PST) From: Robert Foley To: qemu-devel@nongnu.org Subject: [PATCH v2 5/6] Add use of RCU for qemu_logfile. Date: Fri, 15 Nov 2019 08:10:39 -0500 Message-Id: <20191115131040.2834-6-robert.foley@linaro.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191115131040.2834-1-robert.foley@linaro.org> References: <20191115131040.2834-1-robert.foley@linaro.org> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::642 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.puhov@linaro.org, alex.bennee@linaro.org, robert.foley@linaro.org Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" This now allows changing the logfile while logging is active, and also solves the issue of a seg fault while changing the logfile. Any read access to the qemu_logfile handle will use the rcu_read_lock()/unlock() around the use of the handle. To fetch the handle we will use atomic_rcu_read(). We also in many cases do a check for validity of the logfile handle before using it to deal with the case where the file is closed and set to NULL. The cases where we write to the qemu_logfile will use atomic_rcu_set(). Writers will also use call_rcu() with a newly added qemu_logfile_free function for freeing/closing when readers have finished. Signed-off-by: Robert Foley Reviewed-by: Alex Bennée --- v2 - No specific changes, just merging in cleanup changes in qemu_set_log(). --- v1 - Changes for review comments. - Minor changes to definition of QemuLogFile. - Changed qemu_log_separate() to fix unbalanced and remove qemu_log_enabled() check. - changed qemu_log_lock() to include else. - make qemu_logfile_free static. - use g_assert(logfile) in qemu_logfile_free. - Relocated unlock out of if/else in qemu_log_close(), and in qemu_set_log(). --- include/qemu/log.h | 42 +++++++++++++++++++++++---- util/log.c | 72 ++++++++++++++++++++++++++++++++-------------- include/exec/log.h | 33 ++++++++++++++++++--- tcg/tcg.c | 12 ++++++-- 4 files changed, 126 insertions(+), 33 deletions(-) diff --git a/include/qemu/log.h b/include/qemu/log.h index a7c5b01571..528e1f9dd7 100644 --- a/include/qemu/log.h +++ b/include/qemu/log.h @@ -3,9 +3,16 @@ /* A small part of this API is split into its own header */ #include "qemu/log-for-trace.h" +#include "qemu/rcu.h" + +typedef struct QemuLogFile { + struct rcu_head rcu; + FILE *fd; +} QemuLogFile; /* Private global variable, don't use */ -extern FILE *qemu_logfile; +extern QemuLogFile *qemu_logfile; + /* * The new API: @@ -25,7 +32,16 @@ static inline bool qemu_log_enabled(void) */ static inline bool qemu_log_separate(void) { - return qemu_logfile != NULL && qemu_logfile != stderr; + QemuLogFile *logfile; + bool res = false; + + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile && logfile->fd != stderr) { + res = true; + } + rcu_read_unlock(); + return res; } #define CPU_LOG_TB_OUT_ASM (1 << 0) @@ -55,14 +71,23 @@ static inline bool qemu_log_separate(void) static inline FILE *qemu_log_lock(void) { - qemu_flockfile(qemu_logfile); - return logfile->fd; + QemuLogFile *logfile; + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + qemu_flockfile(logfile->fd); + return logfile->fd; + } else { + rcu_read_unlock(); + return NULL; + } } static inline void qemu_log_unlock(FILE *fd) { if (fd) { qemu_funlockfile(fd); + rcu_read_unlock(); } } @@ -73,9 +98,14 @@ static inline void qemu_log_unlock(FILE *fd) static inline void GCC_FMT_ATTR(1, 0) qemu_log_vprintf(const char *fmt, va_list va) { - if (qemu_logfile) { - vfprintf(qemu_logfile, fmt, va); + QemuLogFile *logfile; + + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + vfprintf(logfile->fd, fmt, va); } + rcu_read_unlock(); } /* log only if a bit is set on the current loglevel mask: diff --git a/util/log.c b/util/log.c index 91ebb5c924..9f9b6b74b7 100644 --- a/util/log.c +++ b/util/log.c @@ -28,7 +28,7 @@ static char *logfilename; static QemuMutex qemu_logfile_mutex; -FILE *qemu_logfile; +QemuLogFile *qemu_logfile; int qemu_loglevel; static int log_append = 0; static GArray *debug_regions; @@ -37,10 +37,14 @@ static GArray *debug_regions; int qemu_log(const char *fmt, ...) { int ret = 0; - if (qemu_logfile) { + QemuLogFile *logfile; + + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { va_list ap; va_start(ap, fmt); - ret = vfprintf(qemu_logfile, fmt, ap); + ret = vfprintf(logfile->fd, fmt, ap); va_end(ap); /* Don't pass back error results. */ @@ -48,6 +52,7 @@ int qemu_log(const char *fmt, ...) ret = 0; } } + rcu_read_unlock(); return ret; } @@ -56,12 +61,24 @@ static void __attribute__((__constructor__)) qemu_logfile_init(void) qemu_mutex_init(&qemu_logfile_mutex); } +static void qemu_logfile_free(QemuLogFile *logfile) +{ + g_assert(logfile); + + if (logfile->fd != stderr) { + fclose(logfile->fd); + } + g_free(logfile); +} + static bool log_uses_own_buffers; /* enable or disable low levels log */ void qemu_set_log(int log_flags) { bool need_to_open_file = false; + QemuLogFile *logfile; + qemu_loglevel = log_flags; #ifdef CONFIG_TRACE_LOG qemu_loglevel |= LOG_TRACE; @@ -80,43 +97,47 @@ void qemu_set_log(int log_flags) g_assert(qemu_logfile_mutex.initialized); qemu_mutex_lock(&qemu_logfile_mutex); if (qemu_logfile && !need_to_open_file) { - qemu_mutex_unlock(&qemu_logfile_mutex); - qemu_log_close(); + logfile = qemu_logfile; + atomic_rcu_set(&qemu_logfile, NULL); + call_rcu(logfile, qemu_logfile_free, rcu); } else if (!qemu_logfile && need_to_open_file) { + logfile = g_new0(QemuLogFile, 1); if (logfilename) { - qemu_logfile = fopen(logfilename, log_append ? "a" : "w"); - if (!qemu_logfile) { + logfile->fd = fopen(logfilename, log_append ? "a" : "w"); + if (!logfile->fd) { + g_free(logfile); perror(logfilename); _exit(1); } /* In case we are a daemon redirect stderr to logfile */ if (is_daemonized()) { - dup2(fileno(qemu_logfile), STDERR_FILENO); - fclose(qemu_logfile); + dup2(fileno(logfile->fd), STDERR_FILENO); + fclose(logfile->fd); /* This will skip closing logfile in qemu_log_close() */ - qemu_logfile = stderr; + logfile->fd = stderr; } } else { /* Default to stderr if no log file specified */ assert(!is_daemonized()); - qemu_logfile = stderr; + logfile->fd = stderr; } /* must avoid mmap() usage of glibc by setting a buffer "by hand" */ if (log_uses_own_buffers) { static char logfile_buf[4096]; - setvbuf(qemu_logfile, logfile_buf, _IOLBF, sizeof(logfile_buf)); + setvbuf(logfile->fd, logfile_buf, _IOLBF, sizeof(logfile_buf)); } else { #if defined(_WIN32) /* Win32 doesn't support line-buffering, so use unbuffered output. */ - setvbuf(qemu_logfile, NULL, _IONBF, 0); + setvbuf(logfile->fd, NULL, _IONBF, 0); #else - setvbuf(qemu_logfile, NULL, _IOLBF, 0); + setvbuf(logfile->fd, NULL, _IOLBF, 0); #endif log_append = 1; } - qemu_mutex_unlock(&qemu_logfile_mutex); + atomic_rcu_set(&qemu_logfile, logfile); } + qemu_mutex_unlock(&qemu_logfile_mutex); } void qemu_log_needs_buffers(void) @@ -245,19 +266,28 @@ out: /* fflush() the log file */ void qemu_log_flush(void) { - fflush(qemu_logfile); + QemuLogFile *logfile; + + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + fflush(logfile->fd); + } + rcu_read_unlock(); } /* Close the log file */ void qemu_log_close(void) { + QemuLogFile *logfile; + g_assert(qemu_logfile_mutex.initialized); qemu_mutex_lock(&qemu_logfile_mutex); - if (qemu_logfile) { - if (qemu_logfile != stderr) { - fclose(qemu_logfile); - } - qemu_logfile = NULL; + logfile = qemu_logfile; + + if (logfile) { + atomic_rcu_set(&qemu_logfile, NULL); + call_rcu(logfile, qemu_logfile_free, rcu); } qemu_mutex_unlock(&qemu_logfile_mutex); } diff --git a/include/exec/log.h b/include/exec/log.h index e2cfd436e6..9bd1e4aa20 100644 --- a/include/exec/log.h +++ b/include/exec/log.h @@ -15,8 +15,15 @@ */ static inline void log_cpu_state(CPUState *cpu, int flags) { + QemuLogFile *logfile; + if (qemu_log_enabled()) { - cpu_dump_state(cpu, qemu_logfile, flags); + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + cpu_dump_state(cpu, logfile->fd, flags); + } + rcu_read_unlock(); } } @@ -40,19 +47,37 @@ static inline void log_cpu_state_mask(int mask, CPUState *cpu, int flags) static inline void log_target_disas(CPUState *cpu, target_ulong start, target_ulong len) { - target_disas(qemu_logfile, cpu, start, len); + QemuLogFile *logfile; + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + target_disas(logfile->fd, cpu, start, len); + } + rcu_read_unlock(); } static inline void log_disas(void *code, unsigned long size) { - disas(qemu_logfile, code, size); + QemuLogFile *logfile; + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + disas(logfile->fd, code, size); + } + rcu_read_unlock(); } #if defined(CONFIG_USER_ONLY) /* page_dump() output to the log file: */ static inline void log_page_dump(void) { - page_dump(qemu_logfile); + QemuLogFile *logfile; + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + page_dump(logfile->fd); + } + rcu_read_unlock(); } #endif #endif diff --git a/tcg/tcg.c b/tcg/tcg.c index 0511266d85..4f616ba38b 100644 --- a/tcg/tcg.c +++ b/tcg/tcg.c @@ -2114,9 +2114,17 @@ static void tcg_dump_ops(TCGContext *s, bool have_prefs) } if (have_prefs || op->life) { - for (; col < 40; ++col) { - putc(' ', qemu_logfile); + + QemuLogFile *logfile; + + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + for (; col < 40; ++col) { + putc(' ', logfile->fd); + } } + rcu_read_unlock(); } if (op->life) {