WEBVTT 00:04.790 --> 00:07.190 So guys, now let us discuss that. 00:07.190 --> 00:11.420 If there are any number of threads of a process, then what are the resources? 00:11.450 --> 00:14.600 All those threads share amongst themselves. 00:15.560 --> 00:21.590 So it is also important that we have a conceptual understanding regarding how threads are managed by 00:21.590 --> 00:22.760 the operating system. 00:22.760 --> 00:23.420 Right? 00:23.420 --> 00:27.920 So to start with, an operating system allocates resources to the threads. 00:27.950 --> 00:33.530 Those resources could be memory, it could be CPU, it could be access to the hardware, right? 00:34.240 --> 00:39.970 So if your process has a number of threads, then any thread can demand dynamic memory allocation from 00:39.970 --> 00:42.400 the operating system using malloc and clocks. 00:42.400 --> 00:43.120 Right. 00:43.480 --> 00:49.060 Then it is the responsibility of the operating system also to schedule each of the threads on the CPU. 00:49.090 --> 00:49.840 Right. 00:50.410 --> 00:55.330 Of course, several threads will going to be subjected to context switching, but at the end of the 00:55.330 --> 01:01.510 day it is the scheduling policy of the operating system which will going to decide that, which thread 01:01.510 --> 01:04.510 will going to be allocated, which CPU of the system. 01:06.250 --> 01:11.890 And of course there could be any number of threads which can access peripherals or hardware of the system. 01:11.890 --> 01:12.580 Right? 01:13.200 --> 01:18.570 So it is the responsibility of the operating system to allocate resources to the threads. 01:18.870 --> 01:21.060 All threads are siblings. 01:21.090 --> 01:22.680 Note the word siblings. 01:22.680 --> 01:27.780 There is absolutely no parent child relationship or hierarchy between the threads. 01:27.810 --> 01:32.850 Now, in the previous lecture videos I was addressing thread as primary or child threads. 01:32.850 --> 01:33.450 Right? 01:33.450 --> 01:37.650 And now here I am saying that the thread do not have any parent child relationship. 01:38.100 --> 01:46.110 Now note that I was addressing threads as parent and child threads only to imply that which thread created 01:46.110 --> 01:46.950 which thread. 01:46.950 --> 01:47.670 Right. 01:49.620 --> 01:55.590 Other than that, there is absolutely no parent child relationship between the threads where the parent 01:55.590 --> 02:00.840 child relationship means that a parent thread having extra privileges over child thread. 02:00.870 --> 02:01.620 Right? 02:01.650 --> 02:07.680 For example, there is no such thing like when parent thread dies, then all the child thread of that 02:07.680 --> 02:08.430 parent dies. 02:08.430 --> 02:09.690 There is no such thing. 02:09.720 --> 02:14.070 Every thread has its own separate, isolated life cycle. 02:14.130 --> 02:19.830 If parent thread dies, then there is absolutely no impact on the life of a child thread. 02:20.280 --> 02:24.960 So it simply means that an operating system view all threads as siblings. 02:24.960 --> 02:31.200 So it simply means that every thread has its own life cycle, every thread take a birth, every thread 02:31.200 --> 02:39.090 live, and then every thread eventually dies out and then every thread dies out after it has completed 02:39.090 --> 02:43.260 its job and it dies independent of other threads in the system. 02:43.260 --> 02:44.070 Right? 02:45.800 --> 02:51.740 So, however, there is one exception rule which violates this point, and that rule was that that when 02:51.740 --> 02:57.200 the main thread dies, then all other threads of the process are also terminated. 02:57.200 --> 02:57.920 Right. 02:58.100 --> 03:04.010 Given the fact that this main thread was not terminated using p thread underscore exit API. 03:04.280 --> 03:07.550 So we have already discussed this point in the previous lecture video. 03:07.550 --> 03:08.240 Right. 03:10.190 --> 03:15.140 So in the remaining section of this course, whenever I say that thread, one is the parent and thread 03:15.170 --> 03:16.040 T2 is the child. 03:16.040 --> 03:20.810 It's only means that thread t1 created thread t2 right. 03:20.810 --> 03:26.500 It simply do not imply that thread t1 has some extra privileges over thread t2. 03:26.510 --> 03:27.260 Right. 03:28.010 --> 03:33.920 Now multiple threads of the process share the same virtual address space of the process. 03:33.920 --> 03:34.550 Right. 03:34.580 --> 03:44.120 It simply means that if one thread t1 of a process has an address zero x for for example, then this 03:44.120 --> 03:45.200 virtual address. 03:45.200 --> 03:52.070 If made accessible to other thread of the process t2, then the thread T2 can also read and write into 03:52.070 --> 03:55.820 the memory at address for right. 03:56.570 --> 04:03.200 In other words, if there is a common data structure of the process D, then as long as the address 04:03.200 --> 04:09.110 of the data structure D is available to the thread T1 as well as thread T2, then both the threads can 04:09.110 --> 04:11.390 have equal access to this data structure. 04:11.390 --> 04:12.800 D Right. 04:13.400 --> 04:18.550 So threads of the same process among themselves share the heap memory of the process. 04:18.560 --> 04:24.890 They share the common resources such as sockets, the open file descriptors, the global variables. 04:24.890 --> 04:25.520 Right? 04:25.520 --> 04:31.100 So this is a very common interview questions that you can be asked that what are the resources of the 04:31.100 --> 04:35.570 same process which can be shared by all the threads of that process? 04:35.570 --> 04:40.910 So the answer is heap memory sockets, file descriptors, global variables, etcetera. 04:40.940 --> 04:41.750 Right. 04:41.840 --> 04:46.280 What threads of the same process cannot share is the stack memory. 04:46.310 --> 04:47.170 Right? 04:47.180 --> 04:53.420 Every thread of the same process has its own mutually exclusive stack memory. 04:53.660 --> 05:00.030 A31 has its own stack memory and a thread T2 has its own stack memory. 05:00.060 --> 05:05.160 A thread T1 has no access to the stack memory of the thread T2 and thread. 05:05.190 --> 05:08.790 T2 has no access to the stack memory of thread T1. 05:09.210 --> 05:13.830 The stack memory is something which is very private to the threads. 05:15.830 --> 05:21.740 So in the next lecture video, I have added a lecture video from my other course which explains further 05:21.740 --> 05:27.000 details about how stack memory is managed between threads of the same process. 05:27.020 --> 05:33.080 So this is very important from an interview perspective that you are often asked that what are the resources 05:33.080 --> 05:36.270 which are shared among the threads of the same process? 05:36.290 --> 05:41.690 So these are the resources and what is the resource which is not shared between the threads of the same 05:41.690 --> 05:42.140 process. 05:42.140 --> 05:45.290 So such a resource is a stack memory, right?