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[PATCH v2 6/8] util/oslib-posix: Support concurrent os_mem_prealloc() in
From: |
David Hildenbrand |
Subject: |
[PATCH v2 6/8] util/oslib-posix: Support concurrent os_mem_prealloc() invocation |
Date: |
Fri, 17 Dec 2021 14:46:09 +0100 |
Add a mutex to protect the SIGBUS case, as we cannot mess concurrently
with the sigbus handler and we have to manage the global variable
sigbus_memset_context. The MADV_POPULATE_WRITE path can run
concurrently.
Note that page_mutex and page_cond are shared between concurrent
invocations, which shouldn't be a problem.
This is a preparation for future virtio-mem prealloc code, which will call
os_mem_prealloc() asynchronously from an iothread when handling guest
requests.
Reviewed-by: Pankaj Gupta <pankaj.gupta@ionos.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
util/oslib-posix.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index efa4f96d56..9829149e4b 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -95,6 +95,7 @@ typedef struct MemsetThread MemsetThread;
/* used by sigbus_handler() */
static MemsetContext *sigbus_memset_context;
+static QemuMutex sigbus_mutex;
static QemuMutex page_mutex;
static QemuCond page_cond;
@@ -625,6 +626,7 @@ static bool madv_populate_write_possible(char *area, size_t
pagesize)
void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus,
Error **errp)
{
+ static gsize initialized;
int ret;
struct sigaction act, oldact;
size_t hpagesize = qemu_fd_getpagesize(fd);
@@ -638,6 +640,12 @@ void os_mem_prealloc(int fd, char *area, size_t memory,
int smp_cpus,
use_madv_populate_write = madv_populate_write_possible(area, hpagesize);
if (!use_madv_populate_write) {
+ if (g_once_init_enter(&initialized)) {
+ qemu_mutex_init(&sigbus_mutex);
+ g_once_init_leave(&initialized, 1);
+ }
+
+ qemu_mutex_lock(&sigbus_mutex);
memset(&act, 0, sizeof(act));
act.sa_handler = &sigbus_handler;
act.sa_flags = 0;
@@ -665,6 +673,7 @@ void os_mem_prealloc(int fd, char *area, size_t memory, int
smp_cpus,
perror("os_mem_prealloc: failed to reinstall signal handler");
exit(1);
}
+ qemu_mutex_unlock(&sigbus_mutex);
}
}
--
2.31.1
- [PATCH v2 0/8] virtio-mem: Support "prealloc=on", David Hildenbrand, 2021/12/17
- [PATCH v2 2/8] util/oslib-posix: Support MADV_POPULATE_WRITE for os_mem_prealloc(), David Hildenbrand, 2021/12/17
- [PATCH v2 1/8] util/oslib-posix: Let touch_all_pages() return an error, David Hildenbrand, 2021/12/17
- [PATCH v2 3/8] util/oslib-posix: Introduce and use MemsetContext for touch_all_pages(), David Hildenbrand, 2021/12/17
- [PATCH v2 4/8] util/oslib-posix: Don't create too many threads with small memory or little pages, David Hildenbrand, 2021/12/17
- [PATCH v2 5/8] util/oslib-posix: Avoid creating a single thread with MADV_POPULATE_WRITE, David Hildenbrand, 2021/12/17
- [PATCH v2 7/8] util/oslib-posix: Forward SIGBUS to MCE handler under Linux, David Hildenbrand, 2021/12/17
- [PATCH v2 8/8] virtio-mem: Support "prealloc=on" option, David Hildenbrand, 2021/12/17
- [PATCH v2 6/8] util/oslib-posix: Support concurrent os_mem_prealloc() invocation,
David Hildenbrand <=