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library: refine support for multiple concurrent access

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Our new library's now well protected against potential
problems which arise when a multi-threaded application
opens more than one context within the same API at the
same time. However, with a single-threaded application
designed along those same lines, some problems remain.

So, to avoid potential corruption of some data (which
was classified as local 'static __thread') from those
single-threaded designs, we'll move several variables
to the info structure itself and remove the '__thread'
qualifier. Now they're protected against both designs.

[ we'll not be protected against some multi-threaded ]
[ application that shares a single context yet calls ]
[ that interface from separate threads. this is just ]
[ bad application design & no different than sharing ]
[ other modifiable global data between such threads! ]

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner 2021-11-10 00:00:00 -05:00 committed by Craig Small
parent 126b14470e
commit eafd8e3112
5 changed files with 19 additions and 19 deletions
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6
proc/meminfo.c
View File

@ -135,6 +135,7 @@ struct meminfo_info {
struct stacks_extent *extents;
struct hsearch_data hashtab;
struct meminfo_result get_this;
time_t sav_secs;
};
@ -882,7 +883,6 @@ PROCPS_EXPORT struct meminfo_result *procps_meminfo_get (
struct meminfo_info *info,
enum meminfo_item item)
{
static __thread time_t sav_secs;
time_t cur_secs;
errno = EINVAL;
@ -895,10 +895,10 @@ PROCPS_EXPORT struct meminfo_result *procps_meminfo_get (
/* we will NOT read the meminfo file with every call - rather, we'll offer
a granularity of 1 second between reads ... */
cur_secs = time(NULL);
if (1 <= cur_secs - sav_secs) {
if (1 <= cur_secs - info->sav_secs) {
if (meminfo_read_failed(info))
return NULL;
sav_secs = cur_secs;
info->sav_secs = cur_secs;
}
info->get_this.item = item;

14
proc/pids.c
View File

@ -96,6 +96,8 @@ struct pids_info {
struct stacks_extent *get_ext; // for active 'get' (also within 'extents')
enum pids_fetch_type get_type; // last known type of 'get' request
int seterr; // an ENOMEM encountered during assign
proc_t get_proc; // the proc_t used by procps_pids_get
proc_t fetch_proc; // the proc_t used by pids_stacks_fetch
};
@ -1123,7 +1125,6 @@ static int pids_stacks_fetch (
#define n_alloc info->fetch.n_alloc
#define n_inuse info->fetch.n_inuse
#define n_saved info->fetch.n_alloc_save
static __thread proc_t task; // static for initial 0's + later free(s)
struct stacks_extent *ext;
// initialize stuff -----------------------------------
@ -1140,7 +1141,7 @@ static int pids_stacks_fetch (
// iterate stuff --------------------------------------
n_inuse = 0;
while (info->read_something(info->fetch_PT, &task)) {
while (info->read_something(info->fetch_PT, &info->fetch_proc)) {
if (!(n_inuse < n_alloc)) {
n_alloc += STACKS_GROW;
if (!(info->fetch.anchor = realloc(info->fetch.anchor, sizeof(void *) * n_alloc))
@ -1148,9 +1149,9 @@ static int pids_stacks_fetch (
return -1; // here, errno was set to ENOMEM
memcpy(info->fetch.anchor + n_inuse, ext->stacks, sizeof(void *) * STACKS_GROW);
}
if (!pids_proc_tally(info, &info->fetch.counts, &task))
if (!pids_proc_tally(info, &info->fetch.counts, &info->fetch_proc))
return -1; // here, errno was set to ENOMEM
if (!pids_assign_results(info, info->fetch.anchor[n_inuse++], &task))
if (!pids_assign_results(info, info->fetch.anchor[n_inuse++], &info->fetch_proc))
return -1; // here, errno was set to ENOMEM
}
/* while the possibility is extremely remote, the readproc.c (read_something) |
@ -1404,7 +1405,6 @@ PROCPS_EXPORT struct pids_stack *procps_pids_get (
struct pids_info *info,
enum pids_fetch_type which)
{
static __thread proc_t task; // static for initial 0's + later free(s)
errno = EINVAL;
if (info == NULL)
@ -1432,9 +1432,9 @@ fresh_start:
}
errno = 0;
if (NULL == info->read_something(info->get_PT, &task))
if (NULL == info->read_something(info->get_PT, &info->get_proc))
return NULL;
if (!pids_assign_results(info, info->get_ext->stacks[0], &task))
if (!pids_assign_results(info, info->get_ext->stacks[0], &info->get_proc))
return NULL;
return info->get_ext->stacks[0];
} // end: procps_pids_get

6
proc/slabinfo.c
View File

@ -133,6 +133,7 @@ struct slabinfo_info {
struct fetch_support fetch; // support for procps_slabinfo_reap
struct slabs_node nul_node; // used by slabinfo_get/select
struct slabinfo_result get_this; // used by slabinfo_get
time_t sav_secs; // used by slabinfo_get
};
@ -839,7 +840,6 @@ PROCPS_EXPORT struct slabinfo_result *procps_slabinfo_get (
struct slabinfo_info *info,
enum slabinfo_item item)
{
static __thread time_t sav_secs;
time_t cur_secs;
errno = EINVAL;
@ -852,10 +852,10 @@ PROCPS_EXPORT struct slabinfo_result *procps_slabinfo_get (
/* we will NOT read the slabinfo file with every call - rather, we'll offer
a granularity of 1 second between reads ... */
cur_secs = time(NULL);
if (1 <= cur_secs - sav_secs) {
if (1 <= cur_secs - info->sav_secs) {
if (slabinfo_read_failed(info))
return NULL;
sav_secs = cur_secs;
info->sav_secs = cur_secs;
}
info->get_this.item = item;

6
proc/stat.c
View File

@ -145,6 +145,7 @@ struct stat_info {
struct stat_result get_this; // for return to caller after a get
struct item_support reap_items; // items used for reap (shared among 3)
struct item_support select_items; // items unique to select
time_t sav_secs; // used by procps_stat_get to limit i/o
};
@ -990,7 +991,6 @@ PROCPS_EXPORT struct stat_result *procps_stat_get (
struct stat_info *info,
enum stat_item item)
{
static __thread time_t sav_secs;
time_t cur_secs;
errno = EINVAL;
@ -1003,10 +1003,10 @@ PROCPS_EXPORT struct stat_result *procps_stat_get (
/* we will NOT read the source file with every call - rather, we'll offer
a granularity of 1 second between reads ... */
cur_secs = time(NULL);
if (1 <= cur_secs - sav_secs) {
if (1 <= cur_secs - info->sav_secs) {
if (stat_read_failed(info))
return NULL;
sav_secs = cur_secs;
info->sav_secs = cur_secs;
}
info->get_this.item = item;

6
proc/vmstat.c
View File

@ -236,6 +236,7 @@ struct vmstat_info {
struct stacks_extent *extents;
struct hsearch_data hashtab;
struct vmstat_result get_this;
time_t sav_secs;
};
@ -1376,7 +1377,6 @@ PROCPS_EXPORT struct vmstat_result *procps_vmstat_get (
struct vmstat_info *info,
enum vmstat_item item)
{
static __thread time_t sav_secs;
time_t cur_secs;
errno = EINVAL;
@ -1389,10 +1389,10 @@ PROCPS_EXPORT struct vmstat_result *procps_vmstat_get (
/* we will NOT read the vmstat file with every call - rather, we'll offer
a granularity of 1 second between reads ... */
cur_secs = time(NULL);
if (1 <= cur_secs - sav_secs) {
if (1 <= cur_secs - info->sav_secs) {
if (vmstat_read_failed(info))
return NULL;
sav_secs = cur_secs;
info->sav_secs = cur_secs;
}
info->get_this.item = item;