util/log: Drop manual log buffering

This buffering was introduced during the Paleozoic: 9fa3e853531.

There has never been an explanation as to why we may not allow
glibc to allocate the file buffer itself.  We certainly have
many other uses of mmap and malloc during user-only startup,
so presumably whatever the issue was, it has been fixed during
the preceeding 18 years.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220417183019.755276-2-richard.henderson@linaro.org>

diff --git a/bsd-user/main.c b/bsd-user/main.c
index 88d347d05ebf0962020ea0a0245708b498f42b19..08f43af23512a36b644de312e65738014f2fff2a 100644 (file)
--- a/bsd-user/main.c
+++ b/bsd-user/main.c
@@ -405,7 +405,6 @@ int main(int argc, char **argv)
     }
 
     /* init debug */
-    qemu_log_needs_buffers();
     qemu_set_log_filename(log_file, &error_fatal);
     if (log_mask) {
         int mask;

diff --git a/include/qemu/log.h b/include/qemu/log.h
index 5739c7e6d8192e9094cd0ee9e02c4868db082aa8..ed59ebd4a24ba22c2da04cf637a8f5c3d2b1e41e 100644 (file)
--- a/include/qemu/log.h
+++ b/include/qemu/log.h
@@ -148,7 +148,6 @@ typedef struct QEMULogItem {
 extern const QEMULogItem qemu_log_items[];
 
 void qemu_set_log(int log_flags);
-void qemu_log_needs_buffers(void);
 void qemu_set_log_filename(const char *filename, Error **errp);
 void qemu_set_dfilter_ranges(const char *ranges, Error **errp);
 bool qemu_log_in_addr_range(uint64_t addr);

diff --git a/linux-user/main.c b/linux-user/main.c
index fbc9bcfd5f5f4d4e0f869db8eaff0ecef3daed6e..2b0635068864a16b32ae9dd5bd9d63e866f56243 100644 (file)
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -679,7 +679,6 @@ int main(int argc, char **argv, char **envp)
 
     log_mask = last_log_mask | (enable_strace ? LOG_STRACE : 0);
     if (log_mask) {
-        qemu_log_needs_buffers();
         qemu_set_log(log_mask);
     }
 

diff --git a/util/log.c b/util/log.c
index 2ee1500beedf9630f162454a38333e46b23953b9..ffa66a267e818ff070f7b2624ea8492f46fdf361 100644 (file)
--- a/util/log.c
+++ b/util/log.c
@@ -72,8 +72,6 @@ static void qemu_logfile_free(QemuLogFile *logfile)
     g_free(logfile);
 }
 
-static bool log_uses_own_buffers;
-
 /* enable or disable low levels log */
 void qemu_set_log(int log_flags)
 {
@@ -121,29 +119,18 @@ void qemu_set_log(int log_flags)
             assert(!is_daemonized());
             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(logfile->fd, logfile_buf, _IOLBF, sizeof(logfile_buf));
-        } else {
 #if defined(_WIN32)
-            /* Win32 doesn't support line-buffering, so use unbuffered output. */
-            setvbuf(logfile->fd, NULL, _IONBF, 0);
+        /* Win32 doesn't support line-buffering, so use unbuffered output. */
+        setvbuf(logfile->fd, NULL, _IONBF, 0);
 #else
-            setvbuf(logfile->fd, NULL, _IOLBF, 0);
+        setvbuf(logfile->fd, NULL, _IOLBF, 0);
 #endif
-            log_append = 1;
-        }
+        log_append = 1;
         qatomic_rcu_set(&qemu_logfile, logfile);
     }
 }
 
-void qemu_log_needs_buffers(void)
-{
-    log_uses_own_buffers = true;
-}
-
 /*
  * Allow the user to include %d in their logfile which will be
  * substituted with the current PID. This is useful for debugging many