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Improvements to the design of the /proc lock analysis.

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FossilOrigin-Name: f2809dd3b266c0a6a6eb4ed62812a907493fb4006d26f8905df7ff2b1ca01a5e
This commit is contained in:
drh
2025-10-24 23:12:33 +00:00
parent aeb886bc53
commit 003737d1dc
3 changed files with 113 additions and 120 deletions
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219
src/os_unix.c
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@@ -596,6 +596,108 @@ static struct unix_syscall {
}; /* End of the overrideable system calls */
#if __linux__ && \
(defined(SQLITE_DEBUG) \
|| defined(SQLITE_ENABLE_FILE_INFO) \
|| defined(SQLITE_ENABLE_PAL_ASSERT))
/* ^^^--- Mnemonic: Posix Advisory Lock */
/*
** Examine locking information from the /proc/PID/fdinfo/FD pseudo-file.
**
** If pStr is not NULL, append text that describes the locks to pStr.
**
** if iAssert is not 0, then verify that the there exists an posix
** advisory lock (PAL) on byte iAssert of the file that fd is pointing
** to.
**
** This routine no-ops if /proc/PID/fdinfo/FD cannot be opened.
**
** This routine is intended for diagnostic purposes only and is not a part
** of ordinary builds.
*/
static void unixProcFSLocks(
int fd, /* The file descriptor to analyze */
sqlite3_str *pStr, /* Write a text description of PALs here */
sqlite3_uint64 iAssert /* Assert that this lock is held */
){
int in;
ssize_t n;
char *p, *pNext, *x;
int nLock = 0;
char z[2000];
sqlite3_snprintf(sizeof(z), z, "/proc/%d/fdinfo/%d", getpid(), fd);
in = open(z, O_RDONLY);
if( in<0 ){
if( pStr ) sqlite3_str_appendall(pStr,"(not-available)");
return;
}
n = read(in, z, sizeof(z)-1);
close(in);
if( n<=0 ) return;
z[n] = 0;
pNext = strstr(z, "lock:\t");
while( pNext ){
char cType = 0;
sqlite3_int64 iFirst, iLast;
p = pNext+6;
pNext = strstr(p, "lock:\t");
if( pNext ) pNext[-1] = 0;
if( strstr(p, " READ ")!=0 ){
cType = 'R';
}else if( strstr(p, " WRITE ")!=0 ){
cType = 'W';
}
if( cType==0 ) continue;
x = strrchr(p, ' ');
if( x==0 ) continue;
iLast = strtoll(x+1, 0, 10);
*x = 0;
x = strrchr(p, ' ');
if( x==0 ) continue;
iFirst = strtoll(x+1, 0, 10);
if( pStr ){
const int shmBase = (22+SQLITE_SHM_NLOCK)*4;
if( (nLock++)>0 ) sqlite3_str_append(pStr," ",1);
sqlite3_str_appendf(pStr, "%c ", cType);
if( iFirst>=PENDING_BYTE ){
/* "P+" stands for PENDING_BYTE+ */
sqlite3_str_appendf(pStr, "P+%lld", iFirst - PENDING_BYTE);
}else if( iFirst>=shmBase ){
/* "B+" stands for UNIX_SHM_BASE+ */
sqlite3_str_appendf(pStr, "B+%lld", iFirst - shmBase);
}else{
sqlite3_str_appendf(pStr, "%lld", iFirst);
}
if( iLast>iFirst ){
sqlite3_str_appendf(pStr,"(%lld)", iLast-iFirst+1);
}
}
if( iAssert>=iFirst && iAssert<=iLast ) iAssert = 0;
}
#if defined(SQLITE_ENABLE_PAL_ASSERT) || defined(SQLITE_DEBUG)
if( iAssert ){
sqlite3_snprintf(sizeof(z), z,
"a Posix-advisory lock is missing from byte %lld of fd %d\n",
iAssert, fd);
write(2, z, strlen(z));
abort();
}
#else
(void)iAssert;
#endif
}
#else
# define unixProcFSLocks(A,B,C) /* no-op */
#endif /* __linux__ && (SQLITE_DEBUG || SQLITE_ENABLE_<various>) */
/*
** If compiled with -DSQLITE_ENABLE_PAL_ASSERT, then the ASSERT_PAL_HELD(X,Y)
** macro will print an error on file descriptor 2 and abort if there is
** no PAL on byte Y of file-descriptor x.
*/
#define ASSERT_PAL_HELD(fd,loc) unixProcFSLocks(fd,0,loc)
/*
** On some systems, calls to fchown() will trigger a message in a security
** log if they come from non-root processes. So avoid calling fchown() if
@@ -2119,6 +2221,7 @@ static int posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
lock.l_type = F_UNLCK;
lock.l_whence = SEEK_SET;
lock.l_start = lock.l_len = 0L;
/* ASSERT_PAL_HELD(pFile->h, PENDING_BYTE+2); */
if( unixFileLock(pFile, &lock)==0 ){
pInode->eFileLock = NO_LOCK;
}else{
@@ -3981,119 +4084,6 @@ static int fcntlSizeHint(unixFile *pFile, i64 nByte){
return SQLITE_OK;
}
#if __linux__ && \
(defined(SQLITE_DEBUG) \
|| defined(SQLITE_ENABLE_FILE_INFO) \
|| defined(SQLITE_ENABLE_PROC_ASSERT))
/*
** Examine locking information from the /proc/PID/fdinfo/FD pseudo-file.
**
** If pStr is not NULL, append text that describes the locks to pStr.
**
** if iAssert is not 0, then verify that the byte iAssert/4 is either:
**
** * No locks are held if iAssert%4==0
** * A read-lock is held if iAssert%4==1
** * A write-lock is held if iAssert%4==2
** * Any lock is held if iAssert%4==3
**
** This routine no-ops if /proc/PID/fdinfo/FD cannot be opened.
**
** This routine is intended for diagnostic purposes only and is not a part
** of ordinary builds.
*/
static void unixProcFSLocks(int fd, sqlite3_str *pStr, sqlite3_uint64 iAssert){
int in;
ssize_t n;
char *p, *pNext, *x;
int nLock = 0;
char z[2000];
sqlite3_snprintf(sizeof(z), z, "/proc/%d/fdinfo/%d", getpid(), fd);
in = open(z, O_RDONLY);
if( in<0 ){
if( pStr ) sqlite3_str_appendall(pStr,"(not-available)");
return;
}
n = read(in, z, sizeof(z)-1);
close(in);
if( n>0 ){
z[n] = 0;
pNext = strstr(z, "lock:\t");
while( pNext ){
char cType = 0;
sqlite3_int64 iFirst, iLast;
p = pNext+6;
pNext = strstr(p, "lock:\t");
if( pNext ) pNext[-1] = 0;
if( strstr(p, " READ ")!=0 ){
cType = 'R';
}else if( strstr(p, " WRITE ")!=0 ){
cType = 'W';
}
if( cType ){
x = strrchr(p, ' ');
if( x ){
iLast = strtoll(x+1, 0, 10);
*x = 0;
x = strrchr(p, ' ');
if( x ){
iFirst = strtoll(x+1, 0, 10);
if( pStr ){
const int shmBase = (22+SQLITE_SHM_NLOCK)*4;
if( (nLock++)>0 ) sqlite3_str_append(pStr," ",1);
sqlite3_str_appendf(pStr, "%c ", cType);
if( iFirst>=PENDING_BYTE ){
/* "P+" stands for PENDING_BYTE+ */
sqlite3_str_appendf(pStr, "P+%lld", iFirst - PENDING_BYTE);
}else if( iFirst>=shmBase ){
/* "B+" stands for UNIX_SHM_BASE+ */
sqlite3_str_appendf(pStr, "B+%lld", iFirst - shmBase);
}else{
sqlite3_str_appendf(pStr, "%lld", iFirst);
}
if( iLast>iFirst ){
sqlite3_str_appendf(pStr,"(%lld)", iLast-iFirst+1);
}
}
if( iAssert!=0 ){
if( iAssert/4>=iFirst && iAssert/4<=iLast ){
switch( iAssert%4 ){
case 0:
sqlite3_snprintf(sizeof(z), z,
"byte %lld for fd %d should be unlocked\n",
iAssert/4, fd);
write(2, z, strlen(z));
abort();
case 1:
if( cType=='R' ) iAssert = 0;
break;
case 2:
if( cType=='W' ) iAssert = 0;
break;
case 3:
iAssert = 0;
break;
}
}
}
}
}
}
}
if( iAssert ){
sqlite3_snprintf(sizeof(z), z,
"byte %lld of fd %d should be locked\n",
iAssert/4, fd);
write(2, z, strlen(z));
abort();
}
}
}
#else
# define verifyProcLocks(A,B,C) /* no-op */
#endif /* __linux__ && (SQLITE_DEBUG || SQLITE_ENABLE_<various>) */
/*
** If *pArg is initially negative then this is a query. Set *pArg to
** 1 or 0 depending on whether or not bit mask of pFile->ctrlFlags is set.
@@ -4635,6 +4625,9 @@ static int unixShmSystemLock(
|| (ofst>=UNIX_SHM_BASE && ofst+n<=(UNIX_SHM_BASE+SQLITE_SHM_NLOCK))
);
if( ofst==UNIX_SHM_DMS ){
if( lockType==F_UNLCK && pShmNode->hShm>=0 ){
ASSERT_PAL_HELD(pShmNode->hShm, ofst);
}
assert( pShmNode->nRef>0 || unixMutexHeld() );
assert( pShmNode->nRef==0 || sqlite3_mutex_held(pShmNode->pShmMutex) );
}else{