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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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14
proc/pids.c
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@@ -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