[Qemu-devel] [PATCH][RFT] Fix the regression with SPARC emulation

[Anthony Liguori <aliguori@us.ibm.com>]

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The attached patch should be the proper fix for the sparc performance 
regression.  Unfortunately, this means abandoning signalfd() in favor of 
the signal handler/pipe trick but I don't see another solution to the 
problem.

Please test and let me know if this works for all of your cases (it did 
for me with -clock unix and -clock dynticks).

Regards,

Anthony Liguori

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commit d3e13a91224d167652288ba98de15658a233d60e
Author: Anthony Liguori <anthony@squirrel.(none)>
Date:   Tue Oct 7 17:21:38 2008 -0500

    Replace signalfd with signal handler/pipe.  There is no way to interrupt
    the CPU execution loop when a file descriptor becomes readable.  This
    results in a large performance regression in sparc emulation during
    bootup.
    
    This patch switches us to signal handler/pipe which was originally
    suggested by Ian Jackson.  The signal handler lets us interrupt the
    CPU emulation loop while the write to a pipe lets us avoid the
    select/signal race condition.
    
    Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

diff --git a/compatfd.c b/compatfd.c
deleted file mode 100644
index cc5ced3..0000000
--- a/compatfd.c
+++ /dev/null
@@ -1,127 +0,0 @@
-/*
- * signalfd/eventfd compatibility
- *
- * Copyright IBM, Corp. 2008
- *
- * Authors:
- *  Anthony Liguori   <aliguori@us.ibm.com>
- *
- * This work is licensed under the terms of the GNU GPL, version 2.  See
- * the COPYING file in the top-level directory.
- *
- */
-
-#include "qemu-common.h"
-#include "compatfd.h"
-
-#include <sys/syscall.h>
-#include <pthread.h>
-
-struct sigfd_compat_info
-{
-    sigset_t mask;
-    int fd;
-};
-
-static void *sigwait_compat(void *opaque)
-{
-    struct sigfd_compat_info *info = opaque;
-    int err;
-    sigset_t all;
-
-    sigfillset(&all);
-    sigprocmask(SIG_BLOCK, &all, NULL);
-
-    do {
-        siginfo_t siginfo;
-
-        err = sigwaitinfo(&info->mask, &siginfo);
-        if (err == -1 && errno == EINTR) {
-            err = 0;
-            continue;
-        }
-
-        if (err > 0) {
-            char buffer[128];
-            size_t offset = 0;
-
-            memcpy(buffer, &err, sizeof(err));
-            while (offset < sizeof(buffer)) {
-                ssize_t len;
-
-                len = write(info->fd, buffer + offset,
-                            sizeof(buffer) - offset);
-                if (len == -1 && errno == EINTR)
-                    continue;
-
-                if (len <= 0) {
-                    err = -1;
-                    break;
-                }
-
-                offset += len;
-            }
-        }
-    } while (err >= 0);
-
-    return NULL;
-}
-
-static int qemu_signalfd_compat(const sigset_t *mask)
-{
-    pthread_attr_t attr;
-    pthread_t tid;
-    struct sigfd_compat_info *info;
-    int fds[2];
-
-    info = malloc(sizeof(*info));
-    if (info == NULL) {
-        errno = ENOMEM;
-        return -1;
-    }
-
-    if (pipe(fds) == -1) {
-        free(info);
-        return -1;
-    }
-
-    memcpy(&info->mask, mask, sizeof(*mask));
-    info->fd = fds[1];
-
-    pthread_attr_init(&attr);
-    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
-
-    pthread_create(&tid, &attr, sigwait_compat, info);
-
-    pthread_attr_destroy(&attr);
-
-    return fds[0];
-}
-
-int qemu_signalfd(const sigset_t *mask)
-{
-#if defined(CONFIG_signalfd)
-    int ret;
-
-    ret = syscall(SYS_signalfd, -1, mask, _NSIG / 8);
-    if (ret != -1)
-        return ret;
-#endif
-
-    return qemu_signalfd_compat(mask);
-}
-
-int qemu_eventfd(int *fds)
-{
-#if defined(CONFIG_eventfd)
-    int ret;
-
-    ret = syscall(SYS_eventfd, 0);
-    if (ret >= 0) {
-        fds[0] = fds[1] = ret;
-        return 0;
-    }
-#endif
-
-    return pipe(fds);
-}
diff --git a/compatfd.h b/compatfd.h
deleted file mode 100644
index 55a111a..0000000
--- a/compatfd.h
+++ /dev/null
@@ -1,28 +0,0 @@
-/*
- * signalfd/eventfd compatibility
- *
- * Copyright IBM, Corp. 2008
- *
- * Authors:
- *  Anthony Liguori   <aliguori@us.ibm.com>
- *
- * This work is licensed under the terms of the GNU GPL, version 2.  See
- * the COPYING file in the top-level directory.
- *
- */
-
-#ifndef QEMU_COMPATFD_H
-#define QEMU_COMPATFD_H
-
-#include <signal.h>
-
-struct qemu_signalfd_siginfo {
-    uint32_t ssi_signo;
-    uint8_t pad[124];
-};
-
-int qemu_signalfd(const sigset_t *mask);
-
-int qemu_eventfd(int *fds);
-
-#endif