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CA-407313: Replace semaphore & spinlock with rwlock #26

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merged 6 commits into from
Mar 5, 2025
Merged

CA-407313: Replace semaphore & spinlock with rwlock #26

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5c0050f
CA-407313: Replace semaphore/spinlock with rwlock
Mar 4, 2025
1d6eec8
Update log function descriptions to reflect functionality
Mar 4, 2025
95e5bb3
Address review comments - only hold the rwlock when needed
Mar 4, 2025
66e7fae
Address review comments, use rdlock during sync, add comment to descr…
Mar 4, 2025
0dadb5e
Move fpLogfile NULL check after acquiring the read lock
Mar 4, 2025
92cf64b
Fix second instance of locking after checking for NULL pointer
Mar 4, 2025
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100 changes: 21 additions & 79 deletions daemon/log.c
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Original file line number Diff line number Diff line change
Expand Up @@ -43,8 +43,8 @@
#include <stdarg.h>
#include <string.h>
#include <errno.h>
#include <time.h>
#include <pthread.h>
#include <semaphore.h>
#include <ctype.h>
#include <fcntl.h>
#include <sys/stat.h>
Expand All @@ -58,8 +58,6 @@
#include "log.h"


#define USE_SEMAPHORE 0


#define MTC_LOG_FILE_NAME "/var/log/xha.log"
#define MTC_XHA_MODULE_NAME "xha"
Expand All @@ -73,12 +71,7 @@ static FILE *fpLogfile = NULL;
static MTC_BOOLEAN initialized = FALSE;


#if USE_SEMAPHORE
#define MTC_LOG_SEMAPHORE_NAME "/xha_log_semaphore"
sem_t *semaphore = SEM_FAILED;
#else
static pthread_spinlock_t lock;
#endif
static pthread_rwlock_t lock;


PMTC_S8 monthnames[] = {
Expand Down Expand Up @@ -115,17 +108,10 @@ MTC_S32 log_initialize()
syslog(LOG_WARNING, "can't open local log file. (sys %d)", errno);
}

#if USE_SEMAPHORE
semaphore = sem_open(MTC_LOG_SEMAPHORE_NAME, O_CREAT, S_IRUSR | S_IWUSR, 1);
if (semaphore == SEM_FAILED)
{
syslog(LOG_ERR, "can't open semaphore %s. (sys %d)", MTC_LOG_SEMAPHORE_NAME, errno);
#else
ret = pthread_spin_init(&lock, PTHREAD_PROCESS_PRIVATE);
ret = pthread_rwlock_init(&lock, PTHREAD_PROCESS_PRIVATE);
if (ret)
{
syslog(LOG_ERR, "can't initialize spin lock. (sys %d)", ret);
#endif
syslog(LOG_ERR, "can't initialize rwlock. (sys %d)", ret);
return MTC_ERROR_LOG_PTHREAD;
}

Expand All @@ -141,7 +127,7 @@ MTC_S32 log_initialize()
// This function should be called from ha_log_reopen script
// when log files is rotated.
//
// Smaple logrotate config file </etc/logrotate.d/xha>
// Sample logrotate config file </etc/logrotate.d/xha>
// /var/log/xha.log {
// rotate 5
// size 100k
Expand All @@ -154,17 +140,11 @@ MTC_S32 log_initialize()
// paramaters
//
// return value
// 0: success
// not 0: fail
//

void log_reopen()
{
#if USE_SEMAPHORE
sem_wait(semaphore);
#else
pthread_spin_lock(&lock);
#endif
pthread_rwlock_wrlock(&lock);

if (fpLogfile)
{
Expand All @@ -177,11 +157,7 @@ void log_reopen()
syslog(LOG_WARNING, "can't open local log file. (sys %d)", errno);
}

#if USE_SEMAPHORE
sem_post(semaphore);
#else
pthread_spin_unlock(&lock);
#endif
pthread_rwlock_unlock(&lock);
}


Expand All @@ -199,11 +175,7 @@ void log_terminate()
{
initialized = FALSE;

#if USE_SEMAPHORE
sem_wait(semaphore);
#else
pthread_spin_lock(&lock);
#endif
pthread_rwlock_wrlock(&lock);

if (fpLogfile)
{
Expand All @@ -213,14 +185,8 @@ void log_terminate()

closelog();

#if USE_SEMAPHORE
sem_post(semaphore);
sem_close(semaphore);
sem_unlink(MTC_LOG_SEMAPHORE_NAME);
#else
pthread_spin_unlock(&lock);
pthread_spin_destroy(&lock);
#endif
pthread_rwlock_unlock(&lock);
pthread_rwlock_destroy(&lock);
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I haven't checked the order of cleanup/termination, but destroying the lock can be problematic if other threads try to use it afterwards. I realized that the previous code did this too...

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I'll investigate the clean up order to determine if this can safely be destroyed here

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log_terminate is used once when the threads haven't been setup yet (e.g. if a license check fails), and again after the clean up once each of the threads have been terminated
Therefore destroying the lock during log_terminate is safe

}


Expand Down Expand Up @@ -253,14 +219,10 @@ void log_message(MTC_S32 priority, PMTC_S8 fmt, ...)
return;
}

#if USE_SEMAPHORE
sem_wait(semaphore);
#else
pthread_spin_lock(&lock);
#endif

if (priority & MTC_LOG_PRIVATELOG && fpLogfile != NULL && privatelogflag)
{
pthread_rwlock_rdlock(&lock);

MTC_S32 i = 0;

while (prioritynames[i].c_val != -1 &&
Expand All @@ -271,13 +233,15 @@ void log_message(MTC_S32 priority, PMTC_S8 fmt, ...)

now = time(NULL);
ptm = localtime(&now);
flockfile(fpLogfile);
fprintf(fpLogfile, "%s %02d %02d:%02d:%02d %s %04d [%s] ",
monthnames[ptm->tm_mon], ptm->tm_mday,
ptm->tm_hour, ptm->tm_min, ptm->tm_sec,
ptm->tm_zone, 1900 + ptm->tm_year, prioritynames[i].c_name);

va_start(ap, fmt);
vfprintf(fpLogfile, fmt, ap);
funlockfile(fpLogfile);
va_end(ap);

fflush(fpLogfile);
Expand All @@ -290,20 +254,14 @@ void log_message(MTC_S32 priority, PMTC_S8 fmt, ...)
// fsync(fileno(fpLogfile));
//


pthread_rwlock_unlock(&lock);
}
if ((logmask & MTC_LOG_MASK_SYSLOG) || (priority & MTC_LOG_SYSLOG))
{
va_start(ap, fmt);
vsyslog(LOG_PRI(priority), fmt, ap);
va_end(ap);
}

#if USE_SEMAPHORE
sem_post(semaphore);
#else
pthread_spin_unlock(&lock);
#endif
}


Expand Down Expand Up @@ -332,14 +290,10 @@ void log_bin(MTC_S32 priority, PMTC_S8 data, MTC_S32 size)
return;
}

#if USE_SEMAPHORE
sem_wait(semaphore);
#else
pthread_spin_lock(&lock);
#endif

if (priority & MTC_LOG_PRIVATELOG && fpLogfile != NULL && privatelogflag)
{
pthread_rwlock_rdlock(&lock);
flockfile(fpLogfile);
for (line = 0, pos = 0; pos < size; line++)
{
fprintf(fpLogfile, "\t%04x: ", line);
Expand All @@ -358,20 +312,16 @@ void log_bin(MTC_S32 priority, PMTC_S8 data, MTC_S32 size)

fprintf(fpLogfile, ": %s\n", asc_dmp);
}
funlockfile(fpLogfile);
fflush(fpLogfile);

//
// We don't use fsync(). See comments in log_message().
//
// fsync(fileno(fpLogfile));
//
pthread_rwlock_unlock(&lock);
}

#if USE_SEMAPHORE
sem_post(semaphore);
#else
pthread_spin_unlock(&lock);
#endif
}

//
Expand Down Expand Up @@ -572,18 +522,10 @@ log_fsync()
return;
}

#if USE_SEMAPHORE
sem_wait(semaphore);
#else
pthread_spin_lock(&lock);
#endif
pthread_rwlock_wrlock(&lock);
if (fpLogfile)
{
fsync(fileno(fpLogfile));
}
#if USE_SEMAPHORE
sem_post(semaphore);
#else
pthread_spin_unlock(&lock);
#endif
pthread_rwlock_unlock(&lock);
}