generic-library/bionic
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Prevent deadlock when using fork

Browse Source 
When forking of a new process in bionic, it is critical that it
does not allocate any memory according to the comment in
java_lang_ProcessManager.c:
"Note: We cannot malloc() or free() after this point!
A no-longer-running thread may be holding on to the heap lock, and
an attempt to malloc() or free() would result in deadlock."
However, as fork is using standard lib calls when tracing it a bit,
they might allocate memory, and thus causing the deadlock.
This is a rewrite so that the function cpuacct_add, that fork calls,
will use system calls instead of standard lib calls.

Signed-off-by: christian bejram <christian.bejram@stericsson.com>

Change-Id: Iff22ea6b424ce9f9bf0ac8e9c76593f689e0cc86
This commit is contained in:
Rabin Vincent 2011-04-08 08:50:48 +02:00 committed by Jean-Baptiste Queru
parent e4a21c89a8
commit 177ba8cb42
1 changed files with 16 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
libc/bionic/cpuacct.c
View File

@ -30,16 +30,19 @@
#include <errno.h>
#include <sys/stat.h>
#include "cpuacct.h"
#include <fcntl.h>
int cpuacct_add(uid_t uid)
{
int count;
FILE *fp;
int fd;
char buf[80];
ssize_t n;
int ret = 0;
count = snprintf(buf, sizeof(buf), "/acct/uid/%d/tasks", uid);
fp = fopen(buf, "w+");
if (!fp) {
fd = open(buf, O_RDWR | O_CREAT, 0666);
if (fd == -1) {
/* Note: sizeof("tasks") returns 6, which includes the NULL char */
buf[count - sizeof("tasks")] = 0;
if (mkdir(buf, 0775) < 0)
@ -47,14 +50,19 @@ int cpuacct_add(uid_t uid)
/* Note: sizeof("tasks") returns 6, which includes the NULL char */
buf[count - sizeof("tasks")] = '/';
fp = fopen(buf, "w+");
fd = open(buf, O_RDWR | O_CREAT, 0666);
}
if (!fp)
if (fd == -1)
return -errno;
fprintf(fp, "0");
if (fclose(fp))
n = TEMP_FAILURE_RETRY(write(fd, "0", 1));
if (n < 0)
ret = -errno;
else if (n == 0)
ret = -EIO;
if (TEMP_FAILURE_RETRY(close(fd)) == -1)
return -errno;
return 0;
return ret;
}